Will California weather be impacted by the tropical storm forming near Mexico?
Remnant moisture from soon-to-be Tropical Storm Alvin is forecast to push toward Southern California on Sunday in the wake of a short-lived heat wave, popping thunderstorms and potentially sparking wildfires.
As of Wednesday morning, the tropical storm hasn't fully formed — sustained winds hadn't yet reached the required 39 mph — but a slowing-organizing area of thunderstorms off the southern coast of Mexico is the precursor to Alvin. The National Hurricane Center predicts a nearly 100% chance of a tropical storm developing at some point Wednesday or Thursday.
Alvin would be the first named tropical storm of the season in the northeastern Pacific Ocean. In an average year, that part of the ocean doesn't produce a tropical storm until June 10, but warmer-than-normal water, around 80 degrees, is providing fuel for the forming storm. Alvin won't develop into a full-fledged hurricane, and isn't even forecast to make landfall as a tropical storm, but its moisture will move northward up Baja California on Saturday.
By Sunday, remnant moisture from Alvin is expected to move all the way toward Arizona and parts of Southern California. The moist, unstable air mass could aid in thunderstorms across the Sierra Nevada, Mojave Desert and Transverse Ranges on Sunday.
While Alvin won't affect California the same way Hurricane Hilary did in 2023, areas that don't experience thunderstorms will probably see increased high-altitude clouds, potentially aiding in gorgeous sunrises and sunsets.
A pattern change will bring temps several degrees above normal, with a slight chance of 110+ °F. Tropical moisture will also push up from the south late weekend that will increase rain chances. There's a low chance (5-10%) for some higher end rainfall (>0.50"). #azwx #cawx pic.twitter.com/LpVKAJ2ZcX
— NWS Phoenix (@NWSPhoenix) May 27, 2025
A mix of wet and dry lightning is possible, which could spark a few wildfires. However, vegetation still holds some moisture from winter and spring rains and should limit the potential for large fires.
The Bay Area will probably avoid thunderstorms as an incoming low-pressure system Sunday should deflect the tropical moisture closer to the Sierra.
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Hurricane Erin is one of the fastest rapidly intensifying storms in Atlantic history
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Yahoo
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Hurricane Erin is one of the fastest rapidly intensifying storms in Atlantic history
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The storm is passing just north of the Leeward Islands, the Virgin Islands and Puerto Rico this weekend while making a gradual turn toward the north. It's unlikely it will make a direct landfall on any of the northeastern Caribbean islands, though tropical alerts are in place for some of these areas cautioning potential threats. Erin is forecast to track north over the western Atlantic next week, away from the United States and Bermuda, but that could change if the storm turns more or less sharply than currently forecast. Even if the forecast remains consistent, Erin could cause issues for both places in the form of rough surf and dangerous rip currents. n anticipation of the hurricane, the US Coast Guard captain for the port of San Juan has directed that the ports of St. Thomas and St. John in the US Virgin Islands, and six seaports in Puerto Rico be closed to all inbound vessel traffic unless specifically authorized. 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The first hurricane of the season typically forms around August 11, so Erin was slightly behind schedule, particularly compared to early arrivals in recent seasons. There had already been three hurricanes – Beryl, Debby and Ernesto – by August 15 last year. There will be more chances for tropical systems to develop this month. Longer term forecasts from the Climate Prediction Center highlight the same part of the Atlantic Erin developed in as a place to watch for new storms into at least early September. August is when the tropics usually come alive: The busiest stretch of the season typically spans from mid-August to mid-October. Forecasters expect above-average tropical activity this year. This story has been updated with additional information.
