Fullerton averages 37.5 days a year above 90°F, with February the wettest month at 3.02 in of normal rain. Across decades of records, Sundays are 12% rainier than the weekly average. The hottest day on record was 116°F on Jul 6, 2018; the coldest, 28°F on Jan 14, 2007. The single biggest 24-hour rain event recorded was 2.76 in on Jan 22, 2017.
Climate and Average Weather Year Round in Fullerton
Year-round temperature
In Fullerton, the warmest months are July through October, with average daily highs between 80°F and 87°F. The coldest stretch runs December through February, with highs between 68°F and 69°F and overnight lows reaching 46°F.
Rainfall through the year
Rainfall in Fullerton averages 1.0 in per month over the long run. February is the wettest at 3.0 in, while July is the driest at 0.0 in.
Days at 90 °F or hotter
Fullerton averages 37.5 days per year at 90 °F or hotter. The hottest year on record saw 64 such days (2020); the coolest just 10 (2026).
Precipitation this year
As of May 28, Fullerton has received 5.2 in of precipitation this year — 38% below the long-term normal for this point in the year (8.5 in).