Historical weather data, all-time temperature records, and monthly climate averages for Simi Valley, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in Simi Valley sits in that pleasant shoulder-season sweet spot, with average highs of 76° and lows of 44°. The date has surprised locals before though — temperatures have swung from a freezing 32° in 1998 all the way to a scorching 96° in 1989. Rain is unlikely but not unheard of, with just a 13% chance of any precipitation.
Simi Valley earns its reputation as one of Southern California's hottest inland valleys — its all-time record of 120° set on September 6, 2020 is a number that demands respect. On the other end, a bitter 18° in February 1989 showed the valley can freeze, the same month it picked up its only significant snowfall on record at half an inch.
Simi Valley runs warm nearly year-round, with average highs never dipping below 67° even in the coldest weeks of January. If you're chasing heat, late July through early August is peak season with average highs hitting 97°. Winter is the wet season — such as it is — with the most rainfall concentrated in early February, averaging just over an inch for the week.