Wednesday will be the hottest day of the week, and likely the hottest so far this year in San Francisco, Oakland and San Jose.<\/p>\n
The typically cooling sea breeze will disappear until the mid to late afternoon, if it comes at all. That means downtown San Francisco has a good chance of reaching the low to mid-90s. Even Ocean Beach could reach 80 degrees. Oakland will also be well into the 90s, and San Jose might hit the triple digits. Upper 90s to low 100s are also expected in Wine Country, the Tri-Valley and the Peninsula.<\/p>\n
Wednesday will likely be the hottest day in San Francisco and Oakland since 97- and 100-degree readings in October 2024, respectively.<\/p>\n
Wednesday’s forecast temperatures are made at least five times more likely by climate change, according to Climate Central, a science and communication nonprofit. As humans burn oil, gas, coal, these fossil fuels release heat-trapping carbon dioxide and other pollutants into the atmosphere, warming Earth.<\/p>\n
Exact temperatures will depend on the extent of cloud cover, which is giving California meteorologists headaches this week.<\/p>\n
On Tuesday morning, a line of thunderstorms popped over Los Angeles as moisture from former Hurricane Marie continued to bring rain to Southern California. Those unexpected storms prompted the National Weather Service to quickly revise its forecast, warning of “frequent lighting and brief heavy downpours,” through Tuesday afternoon.<\/p>\n
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Hundreds of lightning strikes approached the Channel Islands on Tuesday afternoon. Thunderstorms were expected to weaken as they moved toward the Bay Area on Wednesday morning, but a few lightning strikes are possible, especially over the Central Coast. (Baron\/Lynx)<\/p>\n
That moisture is forecast to reach the Bay Area early Wednesday. Although thunderstorms are not a guarantee in San Francisco, the surprise lightning in Los Angeles is a sign that the approaching air mass is unsettled and capable of popping storms.<\/p>\n
More likely, the clouds are expected to provide an insulating layer and trap heat at night. Low temperatures Tuesday night are likely to remain in the 60s in much of the Bay Area, including San Francisco. Golden Gate Heights, Twin Peaks, Diamond Heights, the East Bay hills and other elevations above 500 feet may remain in the 70s.<\/p>\n
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Elevated temperatures are expected Tuesday night as most of San Francisco is forecast to be in the mid-60s to low 70s at sunrise Wednesday. (Baron\/Lynx)<\/p>\n
Wednesday night may be even warmer. San Jose may not drop below 70 degrees. Overnight temperatures that high only happen about once per year, on average. Low-lying neighborhoods of San Francisco should remain in the 60s, with hilly neighborhoods in the 70s.<\/p>\n
Warm nights are dangerous for people without air conditioning<\/a> because elevated temperatures prevent human bodies from cooling down from extreme daytime heat. The National Weather Service warns of a major risk of heat-related illnesses across much of the Bay Area on Wednesday, particularly for elderly, infants and people with underlying health conditions.\u00a0<\/p>\n While the clouds will trap heat at night, they may also take a slight edge off temperatures during the day. If overcast conditions prevail into the afternoon, high temperatures will be a few degrees lower than forecast Wednesday.<\/p>\n A significant cooldown is expected Thursday as the sea breeze returns. San Francisco should drop to the 70s, Oakland might not reach 80 and San Jose will be in the upper 80s to low 90s.<\/p>\n Subscribe<\/p>\n There’s more to San Francisco with the Chronicle. Subscribe today for just 25\u00a2.<\/a><\/p>\n