Heat Watch Tuesday: Santa Rosa hits 115, its hottest high on record. Will Wednesday bring a brief cool down?

This live report on the extreme heat will be updated throughout Tuesday with the latest information on forecasts, health information and power grid status. Scroll down for the latest time-stamped updates from Press Democrat journalists covering this breaking story.

Cities in the Bay Area and parts of Northern California Tuesday set “all-time” triple-digit records, according to the National Weather Service.

Downtown Santa Rosa reached 115 degrees outpacing its previous record high of 113, set in 1913, and definitively shattering the daily Sept. 6 record set in 1904 of 106 degrees.

Weather experts described Tuesday as the peak in the weeklong heat wave that looks to be the longest and hottest on record in California.

The high pressure system and heat dome spanning much of California and Great Basin were expected to push other parts of the state to record highs, with heat warnings and advisories extending from the coast all the way to Yellowstone National Park on the Idaho-Wyoming border.

The National Weather Service, which initially said its heat warning covering the Bay Area would end Tuesday, instead extended it to Thursday.

The California Independent System Operator, a Folsom-based nonprofit that oversees the state’s bulk electric power system, issued an energy emergency alert Tuesday afternoon warning of possible rolling blackouts should the stress on the state’s power grid become too much.

Shortly before 7 p.m. in Healdsburg, which operates its own municipal electricity utility and where Tuesday’s high temperature also reached 115 degrees, officials initiated brief blackouts to conserve energy.

By 8 p.m., the state ISO called off its emergency alert saying rolling blackouts weren’t necessary due to customer conservation efforts. Healdsburg quickly ended its rotating outages soon after.

On Wednesday in Santa Rosa and in other parts of Sonoma County, meteorologists are predicting a noticeable cool down with temperatures expected to reach a high of 97. They also are predicting a 20% chance of thunderstorms that will give way to sunshine.

Nighttime lows are expected to drop into the mid 60s.

By Thursday, the temperatures are expected to climb into the triple digits again. In Santa Rosa, the high is expected to be 102 degrees.

8:30 p.m. Healdsburg ends rotating outages, warns of a warm Wednesday

Healdsburg ended its rotating outages in response to the California Independent System Operator giving the all clear.

The announcement was made at 8:10 p.m. on the city’s Facebook page.

It also reiterates that Wednesday is expected to be another hot day and encourages area residents to conserve electricity.

8:10 p.m. State ends energy emergency, thanks Californians

The California Independent System Operator ended its energy emergency at 8 p.m. Tuesday.

In a tweet, the agency reported consumers reduced energy consumption and that eased presser on the electric grid.

Are you in the dark in Healdsburg, Santa Rosa or anywhere else in Sonoma County due to a rolling blackout?

Tell us your story. Send us an email at pdnews@pressdemocrat.com.

7 p.m. Healdsburg announces blackouts to conserve energy

In response to the California Independent System Operator’s mandate, Healdsburg announced it will be shutting off power to parts of the community Tuesday evening.

Power was expected to go off by 7 p.m. for Block 1, which is in the northern part of town, the city announced on Facebook.

It includes homes along Parkland Farms Boulevard and Canyon Run.

Block 2, which is in the center part of the city, was expected to lose power just after 7 p.m. This includes areas on or near Sunnyvale, Poppy Hill and Alexandria drives and Monte Vista Avenue.

Outages are expected to last about an hour per zone.

Healdsburg operates its own municipal utility, which is tied into PG&E lines.

6:55 p.m. It was hotter up north in Mendocino County

If you thought temperatures peaked at 116 degrees within the immediate vicinity of the Bay Area, you’re wrong.

The National Weather Service’s Eureka office reported Ukiah’s high temperature reached 117 degrees ‒ possibly the highest in Northern California.

The reading came from Ukiah Municipal Airport and Mendocino College.

Other areas nearby also reached 116 degrees, but Ukiah was the hottest community falling within the Eureka office’s jurisdiction.

That includes all of Mendocino, Del Norte, Humboldt, Lake and Trinity counties.

6:30 p.m. Santa Rosa wasn’t the only place to set a record

Six Bay Area cities set records or tied previous records Tuesday for their all-time highest temperatures, according to the National Weather Service.

Below are the six cities, their high temperatures on Tuesday and their previous records and years they occurred:

• Santa Rosa: 115 degrees, 113 degrees in 1913;
• Napa: 114 degrees, 113 degrees in 1961;
• Livermore: 116 degrees, 116 degrees on Monday;
• Redwood City: 110 degrees, 110 degrees in 1972;
• San Jose: 109 degrees, 108 degrees in 2017;
• King City: 116 degrees, 115 degrees in 2017.

Below are new records specifically for Sept. 6. These are the cities, their temperatures on Tuesday and their previous records:

• Santa Rosa: 115 degrees, 106 degrees in 1904;
• Napa: 114 degrees, 110 in 2020;
• Half Moon Bay: 81 degrees, 80 in 2004;
• Livermore: 116 degrees, 108 in 1950;
• Redwood City: 110 degrees, 108 in 2020;
• San Jose Airport: 109 degrees, 105 in 2020;
• Gilroy: 113 degrees, 112 in 2020;
• King City: 116 degrees, 110 in 2020.

6:10 p.m. Rolling blackouts possible until 8 p.m.

The California Independent System Operator is requiring rolling blackouts to conserve energy.

The order is in effect until 8 p.m.

“Maximum conservation efforts are urged. During this time, participating customers will be directed by utilities to use generators approved for emergencies, or to reduce load following the protocols of each utility program,“ according to a California ISO alert.

To determine whether you may be subjected to rolling blackouts, click here and type in your address.

5:55 p.m. Flex Alert notifications hit phones

The California Office of Emergency Service issued an alert that set off phones at 5:48 p.m.

The text alert advises “extreme heat continues to stress the power grid. Please conserve energy (Tuesday) after 4 p.m. to reduce the need for power outages.”

PG&E suggests the following measures:

• Set thermostats at 78 degrees or higher, health permitting;
• Once it’s cooler outside, open doors and windows to let it inside;
• Avoid using major appliances;
• Turn off all unnecessary lights;
• Avoid charging electric vehicles.

5:45 p.m. No need to worry about a Red Flag warning

Breezy conditions that cooled the region this afternoon have come and gone.

Just after 5 p.m., National Weather Service meteorgologist Roger Gass verified the region should not anticipate continuous winds that could increase the risk of wildfires.

“There’s no major uptick in winds overall,” he said.

Wednesday should have slightly cooler temperatures even without wind and they’re likely to peak in the upper 90s.

Warmer temperatures are expected to return Thursday, although they won’t be as bad as what developed Tuesday, Gass said.

Sonoma County health officials advice a heat alert is active through 8 p.m. Thursday.

Residents should prepare for rolling blackouts all week due to heavy energy demand, county officials said.

Statewide, residents are encouraged to reduce energy use to ease stress on California’s electrical grid.

5:30 p.m. What happened across the rest of Sonoma County

Below are the high temperatures across the rest of Sonoma County. The National Weather Service wasn’t able to immediately verify whether other communities had record-breaking heat:

• Cloverdale: 116 degrees;
• Healdsburg: 115 degrees;
• Sebastopol: 115 degrees;
• Charles M. Schulz-Sonoma County Airport: 114 degrees;
• Windsor: 114 degrees;
• Rohnert Park: 112 degrees;
• Petaluma: 108 degrees;
• Bodega Bay: 75 degrees.

Onshore winds developed between 2 and 3 p.m. and forecasters say temperatures peaked before then.

4:30 p.m. All-time record falls in Santa Rosa

Santa Rosa hit its hottest-ever recorded temperature on Tuesday amid a blistering, week-long heat wave that again raised the specter of a more dangerous climate era.

The official temperature in Santa Rosa reached 115 degrees, breaking the previous record of 113, set July 11, 1913, according to the National Weather Service. Tuesday’s record also set a new threshold for the hottest daily temperature and the hottest September day since records began in the city in 1902.

In some parts of the county, temperatures were even higher.

The Lake Sonoma Recreation Area saw the mercury hit 118, said Nick Canepa, a meteorologist with the National Weather Service. In most parts of the county, temperatures ranged between 110 and 115 degrees, he added.

3:30 p.m.: Sonoma County sees cool down due to onshore winds

A sudden flow of onshore winds is bringing relief to Sonoma County, dropping temperatures dramatically in places, according to the National Weather Service.

"Essentially the sea breeze kicked in finally,” said Roger Gass, a weather service forecaster. “Basically, it was so warm inland that the onshore flow finally kicked in and brought some southwesterly winds up into up into the interior portions of Sonoma County.”

Gass said some portions of Sonoma County saw a 10-to-15 degree temperature drop within an hour’s time. He said the Petaluma Gap, a saddle in the coastal hills roughly diving parts of Sonoma and Marin counties, allows cooler air masses to come in under the right wind conditions.

“Meanwhile, other valley locations like San Jose, a southwest wind isn’t going to cool them down because they’re so removed from the marine air mass,” he added.

It’s too early to say what was the official high for Santa Rosa. But Gass said an unofficial monitoring station at the Sonoma County Airport did hit between 114 and 115. The previous unofficial high for the airport was 113.

3 p.m. Refuge from the heat at the Sonoma County Library

The sounds of pages turning and keyboards clicking filled the Sonoma County Central Library, as people without access to air conditioning sought refuge in the cooled public building.

“It’s hotter than ever,” said Micah McConnell, 40, who sat at one of the computers with three bottles of cold water, two already drained. He currently does not have housing.

Compared to outside, “this is much better,” he said, drenched in sweat.

McConnell said the weather felt like a reminder that climate change is real and he was worried about the possibility that rising temperatures could lead to catastrophic wildfires like the 2017 Northern California firestorm.

Santa Rosa resident Elvia Parmelee, 70, sat in the library reading “The Girls in Queens: A Novel.”

Parmelee said like many others in Santa Rosa, she does not have air conditioning in her second-floor apartment. When she left her home Tuesday it was 87 degrees inside.

“So here I am cooling off,” she said, adding that she’s been checking in on her older friends experiencing power outages or without AC.

2:30 p.m. Grid operator raises warning on rotating blackouts

California’s grid operator has again raised its warning about the strain on statewide electricity supplies amid the extreme heat, telling consumers “to be prepared for possible outages” this evening.

Electricity demand is expected to reach an all-time high later today, and CAISO, the grid operator expects to declare at 5:30 p.m. a Stage 3 emergency, one step from rotating outages.

Though the state grid operator decides when rotating outages are necessary, you may be notified by text, email or phone before PG&E implements a rotating outage in your area. Such outages typically last one to two hours.

If outages are ordered, find out if your address will be affected at bit.ly/3qik5UY.

2:20 p.m. On the job in Fountaingrove

Midshift handyman Mickey Mosiurchak was pouring ice down his tank top.

Working with a home building crew off of Crown Hill Drive in Fountaingrove, Mosiurchak said the guys were taking frequent breaks — just to sit in the trucks and pump the air conditioning.

“That and Gatorade, water, hosing off my head with a hose,” he said.

His girlfriend brought a load of Gatorade and water for the crew.

And Michael Alguin, owner of Domain Builders where the crew worked, told them to go home at noon.

“We made that call (Monday),” he said.

Going by record breaking temperatures on the Labor Day holiday, he told his crew the shift Tuesday would be short.

“Yesterday was just too hot,” he said. “I’m always watching.”

1:45 p.m. Cooling equipment failure

An air conditioning equipment failure Tuesday morning at Santa Rosa Community Health's pediatric campus on Stony Point Road forced the provider to move operations to its Lombardi campus off Sebastopol Road.

Annemarie Brown, a spokeswoman for SRCH, said repairs on the air conditioner will take place Tuesday night and operations at the pediatric campus should resume Wednesday.

1:30 p.m. Cooling center in Windsor

Windsor's main cooling center is open and has plenty of room. But you won't be able to use the pool. A shortage of lifeguards forced the center to close the pool for the day. The pool will reopen Wednesday and the rest of the week, though 2 pm fitness classes have been canceled to prevent seniors form overexerting.

1:15 p.m. Climate scientist weighs in

During an hourlong briefing on the prolonged heat wave Tuesday, West Coast climate scientist Daniel Swain marveled at temperatures that already were several degrees ahead of where they had been a day earlier, laying the stage for a second day of historic highs and even more sweltering conditions that pose a risk to human health and to the state’s strained energy grid.

But the widespread, extended nature of the extreme heat also raises concerns about the warming of already low flowing streams and rivers and the potential for fish kills, as well as the peril for trees and forests already at risk of drought stress and mortality.

Having the landscaped baked right now also increases the risk of dry lightning that could be produced this weekend or early next week amid atmospheric instability and high-level moisture due to Hurricane Kay, off Baja California, said Swain, a scientist with the Institute of the Environment & Sustainability at UCLA.

1 p.m. From the cool coast, into the broiler

Anne Vernon lives in Timber Cove but was in Santa Rosa Tuesday to meet with clients.

It was 83 degrees on the coast. It was a fair bit hotter in town.

“I was driving and I got out of the car and it was like a walk,” she said. “A wall of heat. It feels almost like a weight.”

Vernon knew the temperatures were soaring just by the sight of more folks flocking to the ocean.

“There are a lot more tourists,” she said. “They are running from the heat.”

12:15 p.m. Taco truck traffic

Janet Marroguin sells chicken and pork tamales on Sebastopol Avenue at Tamales Max. She sold 300 in the early, cool hours but as the heat climbed, sales slowed.

“They stay away,” she said through a Spanish interpreter. “It’s very hot. I’ve sold a couple of tamales, that’s it.”

Next door at Gio y Los Magos, Cristobol Fructuoso started work prepping food for the truck predawn- well before the temperature really started to climb.

Working the stove top making birria tacos at the lunch hour, it was well hotter in the truck.

“I’ve been drinking a lot,” he said. “It’s bad.”

At 12:15, the temperature reads 103.

12 p.m.: Potential power outage in Rohnert Park

The Rohnert Park Department of Public Safety warned residents that PG&E may be required to turn off electricity in Rohnert Park for one to two hours Tuesday if the electrical demand exceeds supply.

They asked residents to try to conserve energy and advised those who need to seek refuge from the heat to go to cooling centers at the senior center and community center.

11:30 a.m.: Spare the Air Alert extended

Due to unhealthy ozone levels over the Bay Area, a Spare The Air Alert was extended through Wednesday. Due to high pressure weather combined with motor vehicle exhaust. On days when the alert is in affect, residents are advised to limit outdoor activities.

In Sebastopol, the Bay Area Air Quality Management District measured fine particulate matter at 30 Tuesday morning, which is considered good. In San Rafael, particulate matter was at 53, which means unusually sensitive people should considered limiting prolonged outdoor exertion.

11:15 a.m.: Providence emergency room seeing no heat-related illnesses

Sonoma County emergency management officials said they were not aware of any heat-related fatalities or serious injuries so far in their coordination with local hospitals and medical providers.

Dr. Chad Krilich, chief medical officer of Providence Santa Rosa Memorial Hospital, said Tuesday morning there have been no significant increase in heat-related illnesses in the hospital’s emergency department.

Krilich encouraged those without access to air conditioning to use community cooling centers where possible.

Krilich also recommended people stay out of the sun, find shade and stay hydrated; leave more strenuous activity for the early morning or later evening hours; and if you feel queasy or dizzy in the heat, stop your activity, find a cooler place and hydrate.

11 a.m.: Power outage reported outside Santa Rosa, Rohnert Park

Pacific Gas & Electric Co. reported 1,160 of its customers had lost power in an outage spanning from the eastern outskirts of Rohnert Park up to the southeastern edge of Santa Rosa.

The outage began at 3:23 a.m. and the estimated restoration time was 12:30 p.m., according to PG&E’s outage map.

9 a.m. Statewide Flex Alert extended

The grid operator, California Independent System Operator extended a statewide Flex Alert Tuesday from 4 to 9 p.m. asking people to voluntarily conserve electricity during peak hours.

(Tips on saving power during a Flex Alert)

It will be the seventh consecutive Flex Alert. The CAISO site Tuesday morning showed California could fall more than 5,000 megawatts short of its power supply at peak demand, forecasted for 4:45 pm.

The state has additional energy capacity at the moment “but blackouts, rolling, rotating outages are a possibility,” said Elliot Mainzer, president of California Independent System Operator, calling additional conservation “absolutely essential.”

The extreme heat was expected to ramp up the risk of rolling blackouts, with state energy officials projecting an electrical load above 51,000 megawatts, the highest demand the state has ever seen.

8 a.m. Schools curtail outdoor activities, sports; half-days for one district

Schools across Sonoma County were prepared to limit outdoor activities and sports on Tuesday amid soaring temperatures.

At Santa Rosa City Schools, the county’s largest district, that included physical education classes being brought indoors and sports practices being canceled, according to district Vanessa Wedderburn.

West county school officials late Monday announced that Analy and Laguna high schools would have a modified, half-day schedule on account of the extreme heat. Other schools in the west county district stuck with regular schedules but modified PE classes to hold them indoors.

6 a.m.: High school runners get an early start

The Santa Rosa High School cross country team held practice at 6 a.m. before the heat kicked in.

“It was fun. It was a great morning,” coach Carrie Joseph said, with a tip of the hat to parents that got kids to the track pre-dawn.

This story includes reporting from the Associated Press.