Sunnyvale averages 16.6 days a year above 90°F, with January the wettest month at 2.8 in of normal rain. The hottest day on record was 109°F on Sep 6, 2022; the coldest, 24°F on Dec 24, 1998. The single biggest 24-hour rain event recorded was 3.23 in on Dec 11, 2014.
Climate and Average Weather Year Round in Sunnyvale
Year-round temperature
In Sunnyvale, the warmest months are June through September, with average daily highs between 79°F and 81°F. The coldest stretch runs December through February, with highs between 60°F and 62°F and overnight lows reaching 42°F.
Rainfall through the year
Rainfall in Sunnyvale averages 1.1 in per month over the long run. January is the wettest at 2.8 in, while July is the driest at 0.0 in.
Days at 90 °F or hotter
Sunnyvale averages 16.6 days per year at 90 °F or hotter. The hottest year on record saw 39 such days (2024); the coolest just 4 (2005).
Precipitation this year
As of May 28, Sunnyvale has received 7.2 in of precipitation this year — 20% below the long-term normal for this point in the year (9.0 in).