After a long stretch of mild, dry days, residents of San Jose and surrounding Silicon Valley are being warned that the last warm spell of November 2025 is about to vanish — replaced by a sudden, brutal shift: rain, howling winds, and freezing temperatures all within a week. It’s not just another autumn transition. This one’s sharp. Unsettling. And potentially damaging to crops, commutes, and comfort.
The Last Warm Breath of Autumn
For now, the sun still lingers. On Cupertino, a tech-heavy suburb just north of San Jose, Climate-Data.org predicts November 3 will be the warmest day of the month — a balmy 21.8°C (71.3°F). That’s sweater weather, not coat weather. People are still eating lunch outdoors. Gardeners are planting bulbs. But behind the scenes, the atmosphere is shifting. The air is getting drier, the nights cooler. And by November 21, the final warm window opens: a three-day stretch — November 21 to 23 — where highs will hover near 20°C, skies clear, and the scent of dry earth lingers.
It’s a deceptive calm. Weather25.com calls it the "last dry period before the storm." Their forecast for San Jose shows only 3 to 8 rainy days total this month — but when they come, they’ll come hard. And then? The freeze.
The Perfect Storm for Farmers
While residents worry about umbrellas and jackets, the real alarm is ringing in orchards. The California Avocado Growers Association, headquartered in the state and representing over 4,000 growers, issued a detailed advisory: November 25 to 27 will bring strong winds and steady rain — 39 mm of precipitation across the region. Then, on November 28 and 29, temperatures will plunge below freezing. Not in the mountains. Not in the high desert. But in the lowlands where avocados, citrus, and young nut trees are still hanging on.
Avocados don’t just dislike frost. They die from it. A single night below 0°C can blacken fruit, collapse cell walls, and wipe out months of labor. Growers in Santa Clara County are already preparing wind machines, wrapping trunks, and moving irrigation schedules. "This isn’t a typical November chill," said one grower who spoke anonymously, fearing market panic. "It’s a 14-degree plunge in under a week. We’ve seen cold snaps before. But never this fast after a warm spell. It’s like someone flipped a switch."
A Weather Pattern That Feels Unnatural
Historically, November in the Bay Area is a slow fade: cooler days, occasional drizzle, gradual frost risk. But this year? The data tells a different story. Climate-Data.org shows Cupertino’s average temperature dropping from 21.8°C on November 3 to just 7.8°C by November 30 — a 14°C fall in just 27 days. And the steepest drop? From 19°C on November 23 to below freezing by November 29.
That kind of volatility isn’t just inconvenient — it’s destabilizing. Urban infrastructure isn’t built for rapid freeze-thaw cycles. Pipes crack. Roads become slick. Elderly residents, already vulnerable to temperature swings, face increased health risks. And for those who’ve spent the last two years adjusting to erratic weather patterns, this feels less like a forecast and more like a pattern.
"We’re seeing more of these rapid transitions," said Dr. Lena Ruiz, a climatologist at Stanford University. "It’s not just global warming making things hotter — it’s making them more erratic. Warm spells are stronger. Cold snaps arrive faster. The system’s losing its rhythm."
What Residents Should Do Now
Weather25.com isn’t mincing words: "Bring along your umbrella so that you don’t get caught in poor weather. Warm clothes are a must." They’re also urging travelers to check the 14-day forecast before heading to San Jose — a rare recommendation for a city that usually has predictable autumn weather.
Here’s what you should do:
- Check your home’s insulation — especially around windows and pipes.
- Keep emergency blankets and bottled water on hand in case of power outages.
- Protect outdoor plants and potted trees — move them indoors if possible.
- If you have pets, limit their time outside during early morning hours.
- Keep your car’s windshield washer fluid rated for freezing temps.
For growers, the stakes are higher. The California Avocado Growers Association is coordinating with state emergency services to deploy frost sensors in key orchards and is urging members to activate irrigation systems during predicted freeze nights — a technique that can raise air temperature by up to 2°C, just enough to save a crop.
What Comes Next?
The freeze is expected to last through December 1, but the bigger question is whether this is an anomaly or a new norm. November 2024 saw a similar — though less severe — spike in late-month freezes. In 2023, the region escaped major frost damage. But 2025? The pattern is too precise, too consistent across multiple agencies, to ignore.
Climate scientists are watching. Farmers are bracing. And residents? They’re learning to pack an extra layer — just in case.
Frequently Asked Questions
How will the freeze affect avocado crops in Silicon Valley?
Avocado trees are highly sensitive to frost. Temperatures below 0°C for even a few hours can cause fruit to blacken and drop, and young trees may die. The California Avocado Growers Association estimates that a single severe freeze event in November could cost growers between $1.2 million and $2.3 million in lost harvests across Santa Clara and San Benito counties. Growers are using wind machines and overhead irrigation to mitigate damage, but success depends on timing and duration.
Why is this weather shift unusual for November in California?
Typically, November brings a gradual cooldown — averaging 1°C to 2°C per week. This year, temperatures are projected to drop over 14°C in just six days, from 21.8°C on November 3 to 7.8°C by month’s end. That’s a rate of change nearly seven times faster than historical averages. Such rapid shifts are becoming more common in climate models, but still rare in real-world observations — making this event noteworthy for meteorologists.
Will it snow in San Jose or Cupertino this November?
No. Weather25.com explicitly forecasts 0 snowy days for San Jose. The valley’s elevation — under 100 meters — and proximity to the Pacific Ocean prevent snowfall. However, freezing temperatures are expected, especially in low-lying areas where cold air settles. Residents may see frost on grass and car windshields, but not snow accumulation.
Are other parts of California experiencing similar conditions?
Yes. The Central Valley, including Fresno and Stockton, is also seeing accelerated cooling and freeze warnings. The coastal regions — like Santa Barbara and Monterey — are experiencing milder conditions due to marine influence, but inland areas are being hit harder. The pattern suggests a broader shift in the state’s late-autumn climate, not isolated to Silicon Valley. The California Avocado Growers Association has issued statewide alerts for growers in Kern, Ventura, and San Diego counties as well.
What should visitors to San Jose pack for late November?
Pack layers — a lightweight waterproof jacket, thermal base layers, a warm hat, and gloves. Even if it’s sunny during the day, temperatures can drop below 10°C by 7 p.m. Avoid thin footwear — wet sidewalks and early frost make walking hazardous. Bring a reusable umbrella and a thermos with hot tea or coffee. Many tourists underestimate how quickly evenings turn chilly here, even in late autumn.
How accurate are these forecasts, given the range of 3 to 8 rainy days?
Forecast ranges like 3 to 8 rainy days reflect uncertainty in atmospheric models — particularly around when the storm front will trigger. But the timing of the warm-to-freeze transition (November 21-29) is consistent across three independent sources: Weather25.com, Climate-Data.org, and the California Avocado Growers Association. That alignment increases confidence in the overall sequence, even if the exact number of rainy days remains uncertain.
