By admin 
Temperatures across the Central Valley will continue to swelter with highs for nearly the entire valley above 100 degrees every day through Sunday.
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Heat advisories have already been issued for the southern portions of the San Joaquin Valley, including Fresno, Merced and Bakersfield, amid high temps reaching close to 110 degrees this weekend. Not only that, but low temperatures in the area will only drop into the mid-70s overnight — and even only to the 80s in the foothills — leading to continual heat stress for anyone spending extended time outside.
Further north in the Sacramento Valley, high temperatures will be a touch cooler but still hot. For the general Delta region and Sacramento, Stockton and Modesto, high temperatures will hover just above 100 degrees as they have the past few days, but could tick up higher Saturday and Sunday as the Delta breeze weakens. Stockton may fare better this Thursday as the Delta breeze remains on and smoke from the Gann Fire to the east delays morning heating.
Further north, temperatures close to 110 degrees will reappear for places like Redding and Chico. Not only will temperatures be well above average for Northern California, with heat advisories issued for the southern Cascades and foothills, but fire will be of particular concern as the afternoon breeze kicks up. These extra winds are thanks to the positioning of a heat dome across northern California, the same pressure ridge that was responsible for the hot weather this past week. The weight of the extra atmosphere will continue to push down toward the surface this weekend.
Wildfire conditions elevated across north California
The hot temperatures led to challenging fire conditions across the state. Earlier this week, the Gann Fire exploded in Calaveras County and has been growing steadily since thanks to an ample supply of fuel and dry air. Afternoon relative humidity values in the teens and lower across the Central Valley have already been observed this week and will continue through the weekend.
Through the weekend, these conditions are expected to persist and even slightly worsen. As the high pressure overhead heats up the air below during the afternoons, that extra heat turns into wind during the late afternoon and evening hours along ridgelines and mountaintops. Wind gusts could exceed 30 mph at times, and any fires that are ongoing, especially those in the Sierra and Northern California, will be at risk of rapidly spreading during the afternoons through Sunday.
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As the high pressure ridge erodes between Saturday and Sunday, winds will roar out of the north over coastal Northern California. This could bring the state more smoke from ongoing fires in Oregon and Washington to the north. This smoke has already entered the Central Valley through the Delta region, and that is expected to continue through the weekend.
Impacts to air quality from the smoke will be marginal for the region. But air quality is already dipping in places in the foothills and higher up in the Sierra due to smoke from the Gann Fire. This includes places like Folsom, and this reduced air quality will reach sensitive levels at times through the weekend as the Gann FIre smoke waxes and wanes in the mountains.
The cooldown arrives next week
Rejoice. Cooler temperatures (in relative terms) are coming in the future. As the high pressure ridge overhead erodes early next week, average temperatures will return by mid-week next week.
That means highs in the low 90s for the Sacramento region and Stockton, and mid- to upper 90s for places such as Merced, Fresno, Modesto, Redding and Chico. That may not seem like a cooldown for some folks, but it will be a noticeable reprieve in heat stress across the entire Central Valley. Low temperatures in the Fresno region could even sink into the 60s after many days of oppressive lows in the mid-70s.
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