CAISO Says High Heat Continues to Pressure California's Grid Into Next Week: How to Read Today's Outlook

What the October 4 post actually says

The account is @CaliforniaISO. The post time on the source record is 2026-10-04T21:58:55.000Z, which is 2:58 p.m. Pacific daylight time on October 4, 2026. The full text is one update line and a pointer:

Oct. 4, 2026 update: High heat continues to impact the state as we head into next week. Visit Today's Outlook for real-time grid conditions.

That is statewide California context from the grid operator that runs the wholesale market and the high-voltage grid for about 80 percent of California and a small part of Nevada, not a city-by-city outage list. The post does not name a county. It does not give a megawatt forecast. It does not say customers will lose power. "High heat continues to impact the state" is a weather and demand statement. "Into next week" reaches past Sunday. Monday, October 5, 2026, is the start of that next week. The action the post asks for is to look at real-time conditions, not to prepare for a shutoff.

Today's Outlook is the public dashboard at https://www.caiso.com/todays-outlook/. The demand view is https://www.caiso.com/todays-outlook/demand. The supply view is https://www.caiso.com/todays-outlook/supply. An older path without the hyphen, /todaysoutlook, was returning 404 when this paper was checked. Use the hyphenated addresses.

What the attached graphic adds

The graphic is branded California ISO and dated 10/4/2026 in the corner. It says that because of forecasted above-normal temperatures and increased electricity demand today and into next week, for California and portions of the West, the ISO is posting more detailed information on its social media platforms. Then it lists five points, in these words:

• The ISO does not forecast any supply shortfalls at this time.
• The current large area of high pressure is expected to remain across the Western US through Thursday.
• Extended period of well-above-normal (10-20 degrees) temperatures are expected across the state.
• Overnight temperatures are expected to be exceptionally warm, limiting overnight cooling.
• Fire weather concerns are observed in Southern California with Santa Ana winds peaking today. A combination of hot temperatures, dry fuels, and gusty winds elevate fire risk.

The graphic then says a Restricted Maintenance Operations (RMO) notice is in place for the California ISO Balancing Authority starting tomorrow, October 5, through Thursday, October 8, for the hours of 10:00 a.m. to 10:00 p.m. each day. It says more detail on the RMO, and the latest system conditions, are on Today's Outlook.

A few reading notes, so the graphic is not stretched past its words:

The "no supply shortfalls at this time" line is the graphic's forecast statement for when it was posted. It is not a promise about Thursday. Forecasts move. The place to see whether that sentence still holds is Today's Outlook and any later ISO notice, not a screenshot from Sunday afternoon.

"Through Thursday" and the RMO end date of Thursday, October 8, 2026, line up. October 4, 2026, was a Sunday. The Thursday after that Sunday is October 8.

The temperature line says "10-20 degrees" above a well-above-normal baseline. The graphic does not print a degree symbol or say Fahrenheit. In U.S. weather briefings that phrase almost always means degrees Fahrenheit. This paper does not add a scale the graphic did not print, and it does not invent city high temperatures the graphic did not give.

"Santa Ana winds peaking today" means Sunday, October 4, 2026, the date printed on the graphic. This paper does not turn that sentence into a county Red Flag Warning list. Fire-weather warnings are National Weather Service products. The graphic is the ISO noting fire weather as a grid concern: hot temperatures, dry fuels, and gusty winds. It does not name a county, a utility public-safety power shutoff, or a fire perimeter.

The graphic does not publish a megawatt number for demand, capacity, reserves, solar, wind, or imports. This paper does not invent those figures. Live megawatt figures on Today's Outlook change through the day. CAISO labels that dashboard as informational. See the section on unofficial numbers below.

Heat stress on the grid is not an outage

Hot weather raises electricity demand because air conditioners run longer. Warm nights matter as much as hot afternoons. When buildings do not cool off overnight, the next day's air conditioning starts from a higher indoor temperature, and some power plants and transmission equipment also get less overnight relief. That is what the graphic is pointing at when it says overnight temperatures will be exceptionally warm and will limit overnight cooling, and when it says demand is expected to be higher today and into next week for California and portions of the West.

Higher demand is not the same sentence as "the power is going out." A grid can be under heat stress and still have enough supply. The graphic says that is the ISO's view at the time of the post: no supply shortfalls forecast. Heat can also raise the chance of equipment trouble and of fire weather affecting lines, which is why operators ask generators and transmission owners to postpone routine maintenance. That request is the Restricted Maintenance Operations notice. It is a step taken so that a hot week is less likely to become a shortfall. It is not itself a shortfall.

CAISO's public emergency-notifications fact sheet says energy shortages can be caused by persistent high heat, equipment failure, weather, or disasters such as wildfires, and that the ISO uses a set of notices when supply is tight. The fact sheet is at https://www.caiso.com/documents/emergency-notifications-fact-sheet.pdf. The notices page that points to it is https://www.caiso.com/emergency-notifications. High heat is a cause the ISO watches. It is not, by itself, one of the emergency labels.

Restricted Maintenance Operations, in plain words

Restricted Maintenance Operations is a CAISO operating notice. It is not a household outage. CAISO's fact sheet describes it this way: when high demand is anticipated, the ISO cautions utilities and transmission operators to avoid taking grid assets offline for routine maintenance, so generators and transmission lines stay available.

Operating Procedure 4420, System Emergency, is the procedure that governs the notice. The public PDF is https://www.caiso.com/documents/4420.pdf. In that procedure, restricted maintenance operations apply to pre-scheduled outages and planned maintenance, and they apply to participating transmission operator control centers, scheduling coordinators, and participating generators, for the hours named in the notice. The procedure says the restriction is used for the shortest duration needed for the reliability concern. A companion procedure, 4420E, lists maintenance that may still be allowed during an RMO if CAISO approves it: https://www.caiso.com/documents/4420e.pdf.

Read against those documents, the October 4 graphic is telling market participants, not residential customers: from Monday, October 5, through Thursday, October 8, between 10:00 a.m. and 10:00 p.m. each day, do not take California ISO Balancing Authority equipment out for routine work if that would reduce what the grid can deliver. Work that does not threaten reliability can still be allowed. CAISO keeps the authority to postpone or cancel work. The hours are daytime and evening, which is when heat-driven demand is highest, not an all-night blackout window.

The graphic says more RMO detail is on Today's Outlook. This paper does not reprint a live banner from that page, because a banner can change after publication. If you need the operator notice itself, look at Today's Outlook and at the system conditions information CAISO posts for market participants. A social graphic is a public summary. It is not a substitute for the notice the control room sends to generators and transmission operators.

What this update did not announce

The ladder of tighter notices is public, and this post did not climb it. Keeping the names straight is the point of this paper.

A Flex Alert is a call for voluntary conservation when the ISO anticipates that supply may not meet high demand. CAISO says cutting use during a Flex Alert can keep the grid from moving into emergency steps. The consumer site is https://www.flexalert.org/. The October 4 post and graphic do not announce a Flex Alert. Do not describe this update as one.

Energy Emergency Alerts follow the North American Electric Reliability Corporation labels the ISO adopted. CAISO's fact sheet, in short, uses these steps:

• EEA Watch: analysis shows available resources are committed or forecast to be in use, and energy deficiencies are expected. It can be issued the day before a projected shortfall, or after a sudden event. Conservation is encouraged.
• EEA 1: real-time analysis shows resources are in use or committed, and deficiencies are expected.
• EEA 2: the ISO is requesting emergency energy and has activated emergency energy programs.
• EEA 3 has a prepare step and an order step. Preparing means reserves cannot be maintained and utilities are told to get ready for rotating outages, but outages have not been ordered. Ordering means the ISO has told utilities to begin rotating outages.

The October 4 graphic says the opposite of a deficiency forecast: no supply shortfalls at this time. It does not use the words Flex Alert, EEA Watch, EEA 1, EEA 2, or EEA 3. It does not say rotating outages are possible, imminent, or underway.

A Transmission Emergency, also on the fact sheet, is for an event that threatens or limits transmission capability, including overloads or outages of lines or equipment. This update does not declare one.

A history of RMOs, Flex Alerts, and emergencies the ISO has actually issued is in the grid-emergencies history report: https://www.caiso.com/documents/grid-emergencies-history-report-1998-to-present.pdf. That file is a record of past events. It is not a forecast for October 5 through October 8, 2026, and this paper does not pull a row out of it and treat it as current.

If a later post does announce a Flex Alert or an EEA, that later post is a different fact. This paper is only about the October 4, 2026, 2:58 p.m. update and the graphic attached to it.

How to read the top of Today's Outlook

Open https://www.caiso.com/todays-outlook/ or the demand page at https://www.caiso.com/todays-outlook/demand. The top block is current and forecasted demand. CAISO's own labels, paraphrased from the page's "About demand" text, are:

Current demand is the power the grid needs right now. The page describes the current-demand figure as a one-minute maximum.

Current capacity is the supply CAISO is counting as available. The page says capacity varies because of startup times, constraints, outages, congestion, and emergencies. It also says the capacity figure does not include solar, wind, or demand-response resources. A capacity number that looks smaller than total generation on a sunny afternoon can be that definition at work, not a hidden shortage. Read the footnote before comparing the two.

Available capacity in the next one to four hours is headroom, not a second copy of current demand. The page says the next-hour figure is the sum of resources' maximum available output minus what they are producing now, including spinning reserve, non-spinning reserve, and regulation-up that is available. It is calculated about every 15 minutes from the real-time pre-dispatch run. The four-hour figure adds remaining battery storage, assuming a full state of charge, and is calculated about every hour from the short-term unit-commitment run. Solar, wind, demand response, and batteries that are already counted as providing reserves are handled under those exclusions. Do not add the solar line from the supply page on top of "available capacity" and call it extra room. The page already told you solar is outside that capacity definition.

Reserves, on a five-minute interval, are spinning reserve, non-spinning reserve, and available regulation-up, including battery storage that is providing reserves. The page says reserves are included in the next-hour available-capacity figure. Reserves are the cushion for a generator or line tripping. They are not unused customer power waiting to be given away, and they are not a sign that customers are already being cut.

Forecasted peak is the most power the ISO expects to need during the day, on a five-minute interval. Tomorrow's forecasted peak is an hourly figure for the next day. The page says the day-ahead forecast is set about 24 hours ahead, from historical load and temperatures, and the hour-ahead forecast is set about an hour ahead. Day-ahead forecast values for the next day through seven days ahead start updating at 5:30 a.m. Pacific time and finish by about 9:30 a.m. Pacific time. A morning reader and an afternoon reader are not looking at the same forecast vintage.

The page also shows a historical peak, the highest demand recorded since the ISO began in 1998, with a link to the historical-peak record. That record is a benchmark. It is not today's number. This paper does not copy the megawatt value, because the dashboard is a live display and because the October 4 post did not state it.

None of these tiles is an outage map. They do not say which neighborhood is without power. An outage at a house is a distribution-utility event. CAISO operates the wholesale system and the high-voltage grid. Your city utility or investor-owned utility is who reports a local outage.

Demand trend and net demand

Under the tiles, the demand trend chart compares system demand, as a five-minute average, with the forecast. Net demand is demand minus wind and solar, also as a five-minute average. On a hot, sunny afternoon, gross demand can be very high while net demand is lower, because rooftop and utility-scale solar are serving a large share of the load. The stress point on a heat wave is often late afternoon and evening, when solar drops and air conditioners are still running. That is why a chart that looks comfortable at 2 p.m. can look tighter at 7 p.m. without anyone having "called an outage." Read the time axis.

The page's how-to-use notes, in short:

Hover a point to see the value at that time of day. Click a name in the legend to hide or show that series. Use the date dropdown to see another day. On today's date, options can show the forecasted peak and yesterday's demand. A download control exports a CSV for the date and series you selected. During a significant demand-response event the demand line can turn red, which the page says means the forecast is pulling away from actual demand because load was reduced. The page says demand response here includes economically dispatched proxy demand resources and reliability demand-response resources that are dispatched economically or manually. It also says reliability demand response may be manually dispatched only if an EEA Watch, an EEA 1, 2, or 3, or a Transmission Emergency is in effect. A red line is a chart flag about an event already called. It is not something this October 4 post created. If you do not see a red line, do not invent one.

Two exclusions matter on both the demand trend and the net-demand trend. The page says those series do not include dispatchable pump loads, and they do not include battery storage that is charging. Pumps and charging batteries are load, but they are not in those two lines. Comparing the demand line to a sum you built from somewhere else will not match, and that mismatch is not evidence of a hidden shortfall.

The supply page

The supply view is https://www.caiso.com/todays-outlook/supply. It shows current demand beside current renewables, hybrids, solar, and wind, then breaks supply into shares and trends.

Current supply is the mix of resources actually delivering power, on a five-minute average, as percentages and as trends. Renewables follow the state Renewables Portfolio Standard definition the page uses: solar, wind, biogas, biomass, and small hydro. Small hydro on that page means under 30 megawatts. Large hydro is 30 megawatts or more and is not inside the renewables slice. Natural gas, nuclear, coal, geothermal, imports, and batteries are their own categories. Imports are power scheduled into the ISO balancing authority from other systems. Batteries are storage: they show up as supply when discharging and, as noted above, charging load is outside the demand-trend line.

Hybrids, on the page's definition, are mixed-fuel resources that share one resource ID at one point of interconnection. The batteries trend shows stand-alone batteries and some hybrids. The page notes that before February 1, 2023, that chart displayed batteries and all hybrids, including their wind and solar components, so older screenshots are not comparable one-for-one with the current chart.

On a hot week the supply page answers a different question than the demand page. Demand says how much power is needed. Supply says what is serving it right now: midday solar, evening gas and imports and batteries, hydro, and the rest. A large solar share at noon does not mean the evening is covered. A large gas share in the evening does not mean the ISO has declared an emergency. It means those units are the ones producing. The October 4 graphic's "no supply shortfalls" line is about whether forecast need exceeds what the ISO expects to have. The supply pie is about the mix, not about that yes-or-no.

Resource adequacy, without turning it into a verdict

Today's Outlook also charts resource adequacy capacity. The page says resource adequacy is capacity the state requires to be bid into the market for reliable operation, minus derates from outages. Capacity needed above that designated amount has to be bought in the real-time market. The seven-day view compares the resource-adequacy forecast for today and the next seven days with the demand forecast plus reserve requirements. The page says the day-ahead reserve requirement shown there is about 1.5 percent of load for estimated regulation reserve plus 6 percent of load for estimated contingency reserves.

Net resource-adequacy capacity subtracts wind and solar resource-adequacy resources. Credits can include demand response and other accounting credits the page lists. Hover for values, use the legend to hide a series, and use the download if you need the CSV. The page says this chart is a way to compare forecasted need with capacity contracted under the resource-adequacy program. It is not a declaration that the lights will stay on or go out. A gap between a forecast line and a resource-adequacy line can mean real-time procurement is expected to fill the difference. It is not, by itself, an EEA.

The October 4 graphic does not quote this chart. Do not read a shape you see on the evening of October 4 back into the graphic as if the ISO printed it.

What the charts are not allowed to be used for

CAISO prints a disclaimer on Today's Outlook. The charts summarize forecasts and actual loads. They are informational only. They should not be used for billing or for operational planning. Data can change without notice. For official market data, the page points to OASIS at https://oasis.caiso.com/. For official emissions data, it points to the California Air Resources Board at https://ww2.arb.ca.gov/.

That disclaimer is why this paper does not paste live megawatt figures. Any number you read on the dashboard after this sentence is unofficial in the sense CAISO itself uses: good for a public snapshot, not a settlement file, and not a number this paper is willing to freeze. If you need a figure for a filing, a contract, or a news story that will still be true next week, pull it from OASIS or from a CAISO notice that states the figure in writing, and cite the timestamp.

The same rule applies to the "10-20 degrees" phrase and the 10:00 a.m. to 10:00 p.m. RMO window. Those words are in the October 4 graphic. They are not a National Weather Service forecast product, and they are not a megawatt study. Quote them as the ISO's social-media graphic, with the post URL, not as an independent weather-service warning.

Fire weather on the graphic, and nothing past it

The graphic says fire weather concerns are observed in Southern California, with Santa Ana winds peaking on October 4, and that hot temperatures, dry fuels, and gusty winds elevate fire risk. Santa Ana winds are offshore winds in Southern California. They dry fuels and can push fire. They can also threaten transmission if a fire starts near a line. That is a grid reason for the ISO to mention them. It is not a list of evacuation zones, and this paper will not invent one.

Check the National Weather Service and local emergency management for fire weather and evacuations. Check your utility for any public-safety power shutoff. Nothing in the October 4 CAISO post text or graphic announces a public-safety power shutoff or a county curtailment. If a utility calls one later, that call will come from the utility, with its own map and times.

What a household should and should not do with this update

You do not need to treat Sunday's post as an order to shut off appliances. No Flex Alert was announced in the post or the graphic. Voluntary conservation on a hot week is a personal choice, not a compliance step this notice created.

If you want to know when a real conservation call or emergency notice does go out, CAISO's emergency-notifications page says people can use the ISO Today app or subscribe to email notifications: https://www.caiso.com/emergency-notifications. That subscription is how you hear the next notice. It is not evidence that an emergency is underway now.

If your lights are out, that is a local outage. Use your utility's outage line or outage map. CAISO does not restore a neighborhood circuit. A heat-wave outlook and a downed service drop are different events that can happen on the same afternoon without being the same event.

If you operate a generator, a factory, or a water system and you take equipment outages through a scheduling coordinator, the RMO hours in the graphic are the sentence aimed at you: routine maintenance that would reduce availability, between 10:00 a.m. and 10:00 p.m. from October 5 through October 8, is what the ISO is asking participants to avoid. Confirm the live notice before you change a work plan. A newspaper-style summary is not the operating instruction.

How this paper will go stale

The useful life of a heat update is days, not years. The graphic's weather window runs through Thursday, October 8, 2026. After that date, the RMO hours it describes should be treated as historical unless a newer notice extends them. The "no supply shortfalls at this time" sentence was true as a statement of the ISO's forecast on the afternoon of October 4, as printed on the graphic. It can be superseded the same day by a Flex Alert, an EEA, or a revised outlook. Before you repeat it, look at https://www.caiso.com/todays-outlook/ and at https://www.caiso.com/emergency-notifications.

This paper will not be silently rewritten into an outage story if conditions worsen. A new notice deserves a new paper. Until then, the accurate headline is the one the ISO used: high heat continues into next week, and the public tool for real-time conditions is Today's Outlook.

Sources

Post text and time: @CaliforniaISO, October 4, 2026, 2:58 p.m. Pacific (2026-10-04T21:58:55.000Z), https://x.com/CaliforniaISO/status/2106866681683365915. The weather bullets, the "no supply shortfalls" sentence, and the October 5 through October 8 Restricted Maintenance Operations hours are from the graphic attached to that post, dated 10/4/2026, not from a separate news release located for this paper.

Today's Outlook, including the definitions of demand, capacity, reserves, net demand, resource adequacy, the chart how-to, and the informational-use disclaimer: https://www.caiso.com/todays-outlook/ and https://www.caiso.com/todays-outlook/demand and https://www.caiso.com/todays-outlook/supply.

Emergency notification definitions, including Flex Alert, Restricted Maintenance Operations, Transmission Emergency, and Energy Emergency Alert steps: https://www.caiso.com/documents/emergency-notifications-fact-sheet.pdf and https://www.caiso.com/emergency-notifications.

Operating procedures: https://www.caiso.com/documents/4420.pdf and https://www.caiso.com/documents/4420e.pdf. Past-event history, not a current forecast: https://www.caiso.com/documents/grid-emergencies-history-report-1998-to-present.pdf. Flex Alert consumer page, for a future call if one is made: https://www.flexalert.org/. Official market data: https://oasis.caiso.com/. Official emissions data, as CAISO points to it: https://ww2.arb.ca.gov/.

Numbers on Today's Outlook are unofficial for billing and operational planning, by CAISO's own disclaimer, and this paper does not freeze them. The temperature band and the RMO clock times are quoted from the social graphic only.

Not legal advice. Not a newspaper. Not Legal Publication. Record of Sale, LLC (Oregon). Notice Nearby is an indexed public paper, not the California ISO and not a utility.

Notes and sources

1. Author: Ryan Standley / Record of Sale, LLC / Notice Nearby.
2. Discussed on @NoticeNearYou: (pending — fill xPostUrl after live post).
3. Not legal advice. Not a newspaper. Not Legal Publication. Record of Sale, LLC (Oregon).