Weather in Irvine in December

Prime time. December is about as good as Irvine gets. Highs average 17.5 °C, lows 13.3 °C, and rain falls on 6 days — nothing in the month is working against you.

December ranks 11 of 12 — near the bottom of Irvine's year. June is the month that works, and the swing between the two is 24 points, which is a different holiday rather than a slightly better one. Worth keeping in perspective: December is the weakest month of Irvine's year and it is still a perfectly good one. The downside here is small.

Rain falls on only 6 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 17.5 °C days and 13.3 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 4.3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 25.7 °C and the coldest night fell to 8.1 °C, and the wettest single day dropped 44 mm — roughly 69% of the month's rain in one day.

This is the volatile part. December rainfall has ranged from 0 mm to 238 mm across the twenty years measured — a 238 mm spread around an average of 64 mm. The average is real but almost no individual December looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 10.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 67%.

How December sits in the year

Temperatures hold steady either side: 20.2 °C in November, 17.5 here, 17.6 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Irvine's year — 9.9 hours of daylight against 14.4 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

Despite being inland, the year stays fairly even: 10.7 °C between the year's warmest afternoons and coldest nights.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

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

December in Irvine versus nearby

If Irvine is one option among several, the nearby comparison is worth making. Riverside is close enough to be a coin toss — 2.3 °C warmer, the same number of rain days. Los Angeles is close enough to be a coin toss — 2.3 °C warmer, the same number of rain days.

So: December is a compromise. June is 20 points better and is what Irvine 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 Irvine

See all twelve months in Irvine, or where else to go in December.