Weather in San Jose in January

A good month. January is a solid month to be in San Jose. Highs average 15.4 °C, lows 5.5 °C, and rain falls on 8 days — nothing in the month is working against you.

January ranks 11 of 12 — near the bottom of San Jose's year. May is the month that works, and the swing between the two is 34 points, which is a different holiday rather than a slightly better one. Worth keeping in perspective: January is the weakest month of San Jose's year and it is still a perfectly good one. The downside here is small.

Rain on 8 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 15.4 °C days and 5.5 °C nights; the spread matters more here than any single number.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest January day reached 24.5 °C and the coldest night fell to -3.8 °C, and the wettest single day dropped 66 mm — roughly 75% of the month's rain in one day.

This is the volatile part. January rainfall has ranged from 0 mm to 309 mm across the twenty years measured — a 309 mm spread around an average of 88 mm. The average is real but almost no individual January looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 5.8 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 84%, high enough to notice on the warm days without dominating them.

How January sits in the year

Temperatures hold steady either side: 15.2 °C in December, 15.4 here, 16.3 in February. Nothing about the timing within the month matters much.

Daylight in January

January sits at the dark end of San Jose's year — 9.9 hours of daylight against 14.7 at midsummer, gaining 0.6 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 12.8 °C in January — too cold to swim without a wetsuit. The sea peaks at 15.4 °C in September and bottoms out at 12.3 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

January in San Jose versus nearby

If San Jose is one option among several, the nearby comparison is worth making. San Francisco is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Napa is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: January is a compromise. May is 27 points better and is what San Jose is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in San Jose

See all twelve months in San Jose, or where else to go in January.