Simi Valley averages 103.5 days a year above 90°F, with February the wettest month at 4.62 in of normal rain. The hottest day on record was 120°F on Sep 6, 2020; the coldest, 18°F on Feb 6, 1989. The single biggest 24-hour rain event recorded was 6.57 in on Nov 29, 1970.
Climate and Average Weather Year Round in Simi Valley
Year-round temperature
In Simi Valley, the warmest months are June through September, with average daily highs between 89°F and 97°F. The coldest stretch runs December through February, with highs between 69°F and 70°F and overnight lows reaching 42°F.
Rainfall through the year
Rainfall in Simi Valley averages 1.4 in per month over the long run. February is the wettest at 4.6 in, while August is the driest at 0.0 in.
Days at 90 °F or hotter
Simi Valley averages 103.5 days per year at 90 °F or hotter. The hottest year on record saw 142 such days (2017); the coolest just 16 (2026).
Precipitation this year
As of May 29, Simi Valley has received 7.7 in of precipitation this year — 36% below the long-term normal for this point in the year (12.1 in).