Even before the heat peaked, all of the signs were there Friday that the stove was turned way up in the Bay Area.

Kids ran around amid spray sprinklers at parks with mothers who fanned themselves in the shade trying to stay cool. Construction workers dumped water on their heads as they endured relentless sun. Waves of heat rose over pavement in the distance.

Almost everyone was seeking relief.

“I didn’t want to melt in my room,” 35-year-old Tiffany Zaguirre of San Jose said as she sat beneath trees at the San Jose Municipal Rose Garden where unofficial temperatures climbed into the mid-80s by 1 p.m. It was a more attractive choice then her home, she said, where the air conditioning was broken.

Temperatures were expected to cool off by a handful of degrees today before descending in all spots to 15-20 degrees cooler than Friday’s anticipated highs. The one exception was likely to be in far eastern Contra Costa County, where the mercury was expected again to hit triple digits.

Still, the brief heat jab acted as most jabs do — as a wake-up call to the harder punches that could come later.

“It is a dangerous day, especially for people who are vulnerable to the heat such as the elderly and small children,” National Weather Service meteorologist Matt Mehle said before the heat peaked. “Since we’re not acclimated to the summer heat yet and it’s such a spike, this is a scenario that could be very impactful for them.”

It also didn’t do the summer fire season any favors.

“When we have fluctuations between intense rainfall in the winter and then hot periods of time in the spring and summer, it changes how the buildup of the vegetation fuels work,” Contra Costa Fire Protection District spokesperson George Laing said. “Also, when you have a lot of rain in the winter, that means a significant growth in shrubs and trees. They all die out faster in the heat. So each of these significant heat events as we have them earlier in the year lead to more aggressive fire behavior later in the year. There is a cumulative effect.”

The weather service anticipated the blanket of heat would rise into triple digits in some areas and into the high 90s in many others Friday, issuing a heat advisory that expired at 8 p.m.

In addition, the Bay Area’s first Spare the Air alert for 2025 also was in effect. The Bay Area Air District issued the alert Thursday in anticipation of what it called unhealthful smog levels.

In Discovery Bay in far eastern Contra Costa County, the dial was expected to hit 102 on Friday, while Antioch also was likely to hit triple digits.

Elsewhere, the weather service showed Concord and Livermore en route to expected highs of 96; Walnut Creek and Pleasanton forecast at 93; and Morgan Hill on its way to a predicted high of 95.

Closer to the coast, San Mateo, Oakland and Richmond all were expected to peak in the high 70s Friday.

At the Rose Garden, Valerie Denise, a 39-year-old Santa Clara resident, also sat in the shade with snacks and drinks. She said she made sure to close her windows and turn on her air conditioning in the morning because she lives on a top-floor residence, where the heat rises from other units.

“I don’t like it,” Denise said of the heat, adding that she had been hoping to stay in bed. “You can put on more blankets to get warmer when you’re cold. You can’t really do (anything) when you’re hot.”

The emergence of high temperatures after winter and spring’s cooler days also challenges the body, safety officials said. People often ignore signs that their body is not adjusting to the heat, such as clammy skin and disorientation.

“That’s a sign to seek cover and get out of the heat right away, because your body is starting to panic,” Laing said. “People don’t pick up on these things, especially when it hasn’t been hot for a while.”

Laing also said that the “most important and common thing that people need to remember is to stay really hydrated all the time, not just when it starts to get hot. Stay out of the heat if you haven’t been in it. And remember proper pool safety.

“It’s the first time kids have been around the pool in a long time, and for some of them, the first time ever. It’s very easy to lose sight of them. They need to be supervised constantly. There should be eyes on them every second.”

This first heat spike of the year won’t be a long one, officials said. In a sense, they said, it will give people some time to adapt to what figure to be longer and warmer stretches this summer.

“The high pressure that’s bringing our heat is fading,” Mehle said. “A trough of low pressure from the Pacific Northwest is going to come across the state and (by Sunday) it’s going to be a blast of that natural air conditioning.”