Heat image by Alexander Grey on unasplash.com

This story was originally published by Fresnoland, a nonprofit news organization. 

San Joaquin Valley residents get a break this week from triple-digit heat – technically.

Temperatures in Fresno could fall as low as 98 or 99 by Friday and into the weekend. Triple-digit heat – and potentially an excessive heat warning, is expected to return Monday, according to the National Weather Service in Hanford.

Extreme heat can be hazardous, especially for farmworkers, construction workers, or others who work without air conditioning.

But as many parts of the world break extreme heat records this July, summer in Fresno – and most of California – has been relatively typical, according to Antoinette Serrato, a meteorologist with the National Weather Service in Hanford.

July has been hot, to be clear – 17 of the 24 days this month have reached triple digits. The average high temperature this month is 101.5 degrees, compared to a normal 97.5.

And there’s been a clear warming trend over the past few decades.

The number of days at or over 100 degrees Fahrenheit in Fresno has increased over the past 75 years that the National Weather Service has collected data, as shown in the chart below.

This year, Fresno has hit just 18 days of triple-digit heat. “We had a bit of a slow start,” added Serrato. Typically, heat waves hit Fresno in May or June – but “we had an impactful winter season.”

Last year, July saw 21 days of triple-digit heat, with a hot August – 22 days – and even a long, early heatwave in September for a total of 65 triple-digit days in 2022. 

But 2021 was worse, with Fresno facing a record-breaking 69 days at or above 100 degrees.

Heatwaves are caused by high-pressure ‘heat domes,’ which can trap hot air in one place. While they can be related to each other in different places, they’re not always connected, said Serrato.

While Fresnans get a quick reprieve from extreme heat over the next few days, everyone should be prepared for a hot August, added Serrato. “After Labor Day, that’s when we’ll stop seeing 100 degrees consistently in the forecast.”