A slow start to the week for coastal California
The week began with classic late spring conditions across coastal California, featuring gray skies, a cool marine layer, and strong afternoon breezes. On Memorial Day, San Francisco barely reached the low 60s °F (around 16–17 °C), while gusty winds—especially near the Golden Gate—made it feel even cooler. The North Bay, East Bay, and South Bay also started off cloudy, with temperatures ranging from the 50s to mid-70s °F (10–24 °C) depending on proximity to the coast.
Midweek transition brings intense inland heat
By Wednesday, a broad ridge of high pressure begins to build across the West, ushering in a sharp and prolonged warming trend. This ridge forms part of a dramatically distorted jet stream pattern stretching across North America, with a deep trough over the East Coast and high pressure intensifying over the West. This setup will pull hot, dry air across California, creating ideal conditions for fire weather, especially in inland valleys.
Triple digits and potential record highs by Friday
Inland California will feel the brunt of this heat by Friday, with cities like Redding projected to reach 107 °F (41.7 °C)—just two degrees shy of its all-time May high. Sacramento is expected to hit 105 °F (40.5 °C), with triple-digit highs extending into parts of the East Bay, including Concord, Livermore, and Napa. Meanwhile, coastal areas will remain mild, with temperatures stuck in the 60s and 70s °F (15–25 °C) under the influence of a persistent marine layer.
Fire weather threats increase near the coast
Forecast models suggest a brief offshore wind event on Friday, which could push inland heat toward the coast. If that occurs, fire danger will rise sharply, especially in brushy hillsides and valleys. This inland-coast heat gradient is typical for late May but the chaotic jet stream and development of a cutoff low over Southern California introduce additional unpredictability. This low could disrupt the heatwave or, alternatively, enhance it depending on its exact position and strength.
Day-by-day breakdown for major Bay Area regions
San Francisco remains cool and breezy, with Monday and Tuesday highs in the low to mid-60s °F (16–18 °C). The Mission District and Potrero Hill may see some late-day sun, but areas like Outer Sunset and Ocean Beach stay cloudy. Winds up to 35 mph through the Golden Gate contribute to a chilly feel.
North Bay areas like Santa Rosa and Napa will gradually warm, reaching the upper 70s °F (25–26 °C) by Tuesday, while the Sonoma and Marin coast remains in the low 60s °F (16–17 °C).
East Bay locations such as Berkeley and Richmond start off foggy, with Tuesday highs in the upper 70s to mid-80s °F (25–29 °C) inland and low 70s °F (21–22 °C) near the Bay shoreline. Concord and Walnut Creek warm significantly, foreshadowing the coming heat.
Pacific Coast and Peninsula cities like Pacifica and Half Moon Bay see minimal sunshine, with highs in the upper 50s °F (14–15 °C). Redwood City and San Mateo will warm slightly on Tuesday, hitting the upper 60s to mid-70s °F (20–24 °C).
South Bay areas like San Jose, Cupertino, and Milpitas begin clearing out on Tuesday, with temperatures rising into the low 80s °F (27–28 °C). Santa Cruz, by contrast, remains partly cloudy, with highs in the low 70s °F (21–22 °C).
Wider implications across the West
This ridge of high pressure won’t stop at the California border. By the weekend, unusually warm temperatures could spread into Alberta and Saskatchewan, intensifying an already dangerous Canadian fire season. This atmospheric pattern reflects a bent and unstable jet stream, which often precedes cutoff lows, heat surges, and even tropical disturbances—a signal of early-season extremes that could unfold unpredictably.
Stay tuned as the Western U.S. enters its first major heat event of 2025, and fire weather risks escalate alongside rapidly rising inland temperatures.
