‘Nastier’ heat waves possible for Northern California this summer. Here’s the latest outlook

Predicting the weather can be a bit like trying to catch the wind.

Meteorologists thought May would be cool and rainy — but only 0.28 inches of rain has fallen since the beginning of the month, there’s no chance of precipitation in the latest forecasts and the heat index hit 100 by mid-May.

Last year, experts said we’d have a dry winter.

We all know how that went.

One thing is clear: With climate change, weather patterns are becoming more intense and unpredictable.

As Sacramento heads into another summer — it’s hard to imagine what the season will hold, especially after facing record-topping, triple-digit heat last September.

Temperatures in the Sacramento area have been teetering in the 80s and 90s with the latest forecast reaching up to 94 degree highs, according to the National Weather Service.

And if Dr. Paul Ullrich, professor of regional and global climate modeling, was going to Las Vegas and had to put a bet down, he’d say it’s going to get hotter.

“With global warming, we’re seeing temperatures rising faster than ever before,” Ullrich said. “And as a consequence, it feels almost like every year is warmer than the last.”

Will we have another heatwave?

Meteorologists are predicting higher-than-normal temperatures this summer.

In a three-month outlook for June-July-August, according to the National Weather Service’s Climate Prediction Center, temperatures for most of California are leaning above average. For July-August-September, temperatures are likely above normal, too.

The average temperature high for the Sacramento area for the summer is about 93 degrees, data from the National Oceanic and Atmospheric Administration shows. In June, average highs are near 88 degrees, July is near 93, August is around 92 and September is near 89.

But triple digits are known to scorch the region in the summertime. Last year, temperatures rose to a record 116 degrees and put Sacramento in one of the longest heat waves it’s ever seen.

There’s a good chance heat waves are coming back this summer — with the highest risk from July to the beginning of September, Ullrich said.

While winter downpours revived parts of the state from drought by replenishing soil, they may have set the stage for a more humid heat — atypical of the Sacramento region.

The water in the soil will act as a buffer against extremely high temperatures, Ullrich said, and will absorb the heat and regulate temperatures.

But this could also produce a lot of humidity and raise the heat index.

Heat index, or apparent temperature, is how temperatures feel like when humidity is mixed with air temperature, according to the weather service. It’s also what is typically used to assess how extreme a heat wave is, with 80-90 degrees classified as “Caution,” 90-103 degrees as “Extreme Caution” and 103-124 degrees as “Danger.” If temperatures are at 125 degrees or higher, it is considered “Extreme Danger” and heat strokes are highly likely.

“So if we have a lot of near surface humidity because of evaporation of the soil moisture, then we’re going to have nastier heat waves,” Ullrich said.

“Or at least heat waves that have greater risk for human health because it affects our ability to basically deal with that heat.”

What are experts predicting for wildfires?

This year’s risk will vary depending on the region, wildfire experts say, due to the different effects the winter downpour had on forests and grasslands.

Ullrich said there’s evidence suggesting that high soil moisture will make it difficult for wildfires to set off in forested regions.

“Hopefully, at least we’re going to be able to leverage this wet winter to have a relatively benign wildfire season up in the Sierras,” he said.

But grassland and wildland-urban interfaces, which are areas between unoccupied land and cities, have some risk because they dry out faster and have a lot vegetation growth to fuel the flames.

This story was originally published May 19, 2023 at 5:00 AM with the headline "‘Nastier’ heat waves possible for Northern California this summer. Here’s the latest outlook."