Weather in San Francisco in April

Prime time. April is about as good as San Francisco gets. Highs average 17.4 °C, lows 8.8 °C, and rain falls on 6 days — nothing in the month is working against you.

April ranks 7 of 12 in San Francisco: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain falls on only 6 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 17.4 °C days and 8.8 °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 April day reached 30.1 °C and the coldest night fell to 3.6 °C, and the wettest single day dropped 35 mm — roughly 83% of the month's rain in one day.

This is the volatile part. April rainfall has ranged from 3 mm to 136 mm across the twenty years measured — a 133 mm spread around an average of 42 mm. The average is real but almost no individual April looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 8.7 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 80%, high enough to notice on the warm days without dominating them.

How April sits in the year

Temperatures hold steady either side: 16.3 °C in March, 17.4 here, 19.6 in May. Nothing about the timing within the month matters much.

Daylight in April

13.1 hours of daylight, gaining 1.2 hours across the month. That is between San Francisco's extremes of 14.8 and 9.6 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 12.2 °C in April — too cold to swim without a wetsuit. The sea peaks at 15.7 °C in September and bottoms out at 12.2 °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

Shoulder. The value months — prices ease off and you get the place closer to itself.

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

April in San Francisco versus nearby

If San Francisco is one option among several, the nearby comparison is worth making. Napa is close enough to be a coin toss — 2.8 °C warmer, the same number of rain days. San Jose is close enough to be a coin toss — 2.6 °C warmer, the same number of rain days.

So: April is a compromise. July is 19 points better and is what San Francisco 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 Francisco

See all twelve months in San Francisco, or where else to go in April.