California is bracing for what could be the hottest day of the year so far, as a prolonged heat wave intensifies across the Sacramento Valley and much of Northern California. Temperatures on Friday are expected to soar to dangerous levels, with Redding forecast to reach a blistering 110°F (43°C) and Sacramento not far behind at 105°F (40.5°C) — the highest readings since last summer.
While the Bay Area will escape the worst of the heat thanks to a steady marine breeze, the inland areas are still facing well-above-average warmth, with temperatures climbing into the 90s (32–37°C) and possibly hitting 100°F (38°C) in spots like Livermore, Concord, Antioch, Brentwood, and Vacaville.
Heat advisories extended through early next week
The National Weather Service has extended a heat advisory for the northern Sacramento Valley through 11 p.m. Monday, as triple-digit temperatures show no signs of letting up. Overnight conditions won’t bring much relief either — lows in Redding and Chico will only dip into the 70s (21–26°C).
A separate advisory is also in effect for the San Joaquin Valley, running from Friday morning through Tuesday night, where highs could reach up to 105°F (40.5°C). Lake County and the interior regions of Mendocino and Humboldt counties are expected to see similar extremes. In Ukiah, the mercury could top out at 105°F (40.5°C).
Even the Sierra Nevada won’t escape the blast of heat — Lake Tahoe is expected to reach 90°F (32°C) over the weekend, marking its hottest stretch since July 2024.
San Francisco: coastal fog keeps the city cool
While much of the state swelters, San Francisco will remain relatively mild thanks to a strong onshore breeze. By midday Thursday, Ocean Beach was stuck in the upper 50s (14–15°C), while the Mission District was basking in the low 70s (21–23°C) — a pattern that will likely repeat on Friday.
Evening winds should strengthen, helping to drop temperatures into the 50s (10–13°C) overnight, except at higher elevations. By Saturday, winds will shift out of the south, gusting up to 25 mph in coastal neighborhoods like Sunset and Richmond, keeping daytime highs in the low 60s (15–17°C).
East of Twin Peaks, skies will clear earlier, and highs will climb into the mid- to upper 60s (18–20°C). Sunday is expected to bring similar conditions, with slightly more morning fog and lows again in the mid-50s (12–13°C).
North Bay: smoky skies and sweltering highs
Much of the North Bay will wake up to hazy skies Friday, the result of smoke from distant wildfires. Despite the haze, sunshine will filter through and push highs into the mid-80s (29°C) in Mill Valley, Vallejo, and Petaluma, with San Rafael and Napa climbing into the upper 80s (31°C).
Farther inland, Santa Rosa, Sonoma, and St. Helena will sizzle in the mid-90s (35°C), while Fairfield and Vacaville could brush up against 100°F (38°C). On the coast, fog and sun will battle it out, keeping beach temperatures in the 60s (16–20°C). Lows overnight will range from the mid-50s to low 60s (13–17°C).
Saturday will bring some relief, with south-southwesterly winds cooling most areas by about 5 to 10 degrees, knocking inland highs back into the 80s to low 90s (27–33°C). A deeper marine layer on Sunday will bring broader cooling, except in the northern Napa Valley and eastern Solano County, where highs will still reach the upper 80s to mid-90s (31–35°C).
East Bay: heat lingers, haze returns
Residents in the East Bay will continue to deal with hazy skies Friday, especially east of the Caldecott Tunnel, where air quality could degrade to moderate or worse. Still, most of the region will see plenty of sunshine.
Highs will hover in the 70s to mid-80s (21–29°C) near the bay, and climb into the upper 80s to low 90s (31–33°C) in Martinez and the Lamorinda area. Inland valleys could easily hit mid-90s to low 100s (35–38°C). Evening breezes from the southwest will gust to about 15 mph, helping to cool things down slightly overnight to the mid-50s to low 60s (13–16°C).
Saturday may bring a bit of morning fog, especially near the Berkeley Hills, followed by a modest cool-down. Daytime highs will fall back to the 70s to low 80s (21–27°C) near the water and upper 80s to mid-90s (31–35°C) further inland. Sunday looks similar, with slightly cooler highs and widespread morning cloud cover. Nights will remain comfortably cool in the mid- to upper 50s (13–15°C).
Peninsula and coast: stark temperature divide
Friday brings a sharp contrast between foggy coastal zones and much warmer inland areas along the Peninsula. Beaches will struggle to get out of the upper 50s to low 60s (14–17°C), while the bay shoreline sees highs in the mid-70s to mid-80s (24–29°C). Foothill towns like Woodside will flirt with 90°F (32°C). Overnight lows will dip into the mid-50s (12–13°C) with patchy fog.
Saturday’s moderate southerly winds will keep the coastline foggy and cool, with gusts up to 25 mph. Inland, however, it will stay sunny and warm, with South San Francisco in the upper 60s (20°C) and Redwood City in the mid-80s (29°C). Sunday should follow a similar pattern, though the morning fog may become more widespread. Overnight lows will remain in the mid-50s (13°C).
South Bay and Santa Cruz: inland heat, coastal cool
In the South Bay, Friday promises to be another hot one, with the southern Santa Clara Valley hitting the mid-90s (35°C). Cities like Palo Alto, Mountain View, and Milpitas will be slightly cooler, in the upper 80s to low 90s (31–33°C).
Down by the coast, Santa Cruz will enjoy a milder day — low 70s (21–22°C) at the beach and low 80s (27°C) near UC Santa Cruz. Scotts Valley should top out in the mid-80s (29°C), while Boulder Creek and Ben Lomond hit the upper 80s to low 90s (31–33°C). Overnight lows will stay near 60°F (16°C) in the valley, but vary more widely in the mountains, from the 50s (12–13°C) in lower elevations to near 70°F (21°C) at the highest peaks.
Cooling is on the way this weekend for Santa Cruz County, with winds off Monterey Bay ushering in denser fog and cooler air. Highs will fall to the 60s at the beaches (16–20°C) and 70s to low 80s (21–27°C) in the hills. Meanwhile, the Santa Clara Valley will stay warm and dry, with highs still in the 80s (27–30°C) thanks to downslope winds. Nights will cool to the mid-50s (13°C).
