Weather in San Diego in May

Prime time. If you get to pick your dates, May is the one. Highs average 25.4 °C, lows 14.4 °C, and rain falls on 1 days — nothing in the month is working against you.

May is the highest-scoring month of the twelve. The nearest rival is April, and the month at the other end of the year is August.

Rain falls on only 1 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: 6 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest May day reached 37.8 °C and the coldest night fell to 9.9 °C.

This is the volatile part. May rainfall has ranged from 0 mm to 45 mm across the twenty years measured — a 45 mm spread around an average of 8 mm. The average is real but almost no individual May looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 8.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 68%.

How May sits in the year

The month is on the way up: 2.1 °C warmer than April, and June adds another 3 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in May

May is at or near the longest days of San Diego's year: 13.8 hours of daylight, gaining 0.7 hours across the month. Evenings are the real gain — dinner outdoors still happens in full light.

Sea temperature

The sea sits at about 16.4 °C in May — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 20.3 °C in September and bottoms out at 15.3 °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

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, February is the trade worth considering — 12 points weaker on weather, and materially quieter.

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

May in San Diego versus nearby

If San Diego is one option among several, the nearby comparison is worth making. Irvine is close enough to be a coin toss — 6.7 °C cooler, the same number of rain days. Riverside is the weaker option in May — 3.6 °C warmer, 1 day more rain.

So: May is the answer for San Diego. If it is booked out or priced out, April is the next best thing at 3 points behind, and August is the month to keep off the shortlist.

Every month in San Diego

See all twelve months in San Diego, or where else to go in May.