The first day of triple-digit temperatures could arrive in Fresno as soon as Friday, although there’s a good chance we’ll only “flirt” with 100-degree weather this week, according to meteorologist Carlos Molina of the National Weather Service in Hanford.

The South Valley and the west side, including Hanford and Lemoore, likely will top the century mark by the end of the week, he said Tuesday.

Next week, there’s a better chance for Fresno’s temperatures to hit 100 by Wednesday or Thursday, Molina said.

Is that later than normal? Not necessarily. According to National Weather Service records, from 1887 through 2021 the average first day of triple-digit temperatures here was June 4. Over the past 10 years, the start of 100-degree weather occurred in May in six years and in June for the other four. The earliest date over the past decade was May 12 in 2013, and the latest was June 30 last year.

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What Accounts for the Valley’s Nice Spring?

Why is this spring comparatively balmy? Molina credits a continuing series of disturbances in the Pacific Northwest that have pushed southward and then lowered daytime high temperatures for a couple of days.

After temperatures climb by the end of this week, the latest Pacific Northwest disturbance will cause a cooldown to near 90 on Sunday and Monday in Fresno before temperatures head upward again toward 100, he said. Because there is no humidity predicted, nighttime lows should be about 20 to 30 degrees cooler than daytime highs.

What kind of summer can we expect?

Molina says there’s a high probability for a heat wave to park over west Texas, New Mexico and maybe eastern Arizona.

When the heat dome stays over that portion of the Southwest, “it’ll kind of prevent California from having a strong heat wave, because cold air is drawn (eastward) towards the warm air,” Molina said. The long-term forecast for June, July, and August is for more extreme heat to remain east of California, he said.

But even if temperatures are “only” in the 90s, there is still a risk of heat impacts, Molina said. He advises residents to stay hydrated and try to do their outdoors activities earlier in the day or later in the evening.