Weather in Napa in May

Prime time. If you get to pick your dates, May is the one. Highs average 24.9 °C, lows 10.8 °C, and rain falls on 3 days — nothing in the month is working against you.

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

Rain falls on only 3 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: 5 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest May day reached 39.2 °C and the coldest night fell to 3.5 °C, and the wettest single day dropped 33 mm — roughly 150% of the month's rain in one day.

This is the volatile part. May rainfall has ranged from 0 mm to 95 mm across the twenty years measured — a 95 mm spread around an average of 22 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 6.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 69%.

How May sits in the year

The month is on the way up: 4.7 °C warmer than April, and June adds another 5.6 °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

14.2 hours of daylight, gaining 0.9 hours across the month. That is between Napa's extremes of 14.8 and 9.5 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 28.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage. Within May itself the daily swing is 14.1 °C, so mornings and afternoons need different clothes.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

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

May in Napa versus nearby

If Napa is one option among several, the nearby comparison is worth making. San Francisco is close enough to be a coin toss — 5.3 °C cooler, the same number of rain days. Sacramento is close enough to be a coin toss — 2.3 °C warmer, the same number of rain days.

So: May is the answer for Napa. If it is booked out or priced out, October is the next best thing at 0 points behind, and December is the month to keep off the shortlist.

Every month in Napa

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