Historical weather data, all-time temperature records, and monthly climate averages for Rosemont, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5th in Rosemont sits right in the sweet spot of spring — historically mild, with an average high of 69° and low of 48° across 148 years of records. There's about a 1-in-4 chance of seeing some rain, though snow has never been a factor on this date. The range of possibilities is wide: it's hit as warm as 88° (1985) and dipped as cold as 36° back in 1929.
Rosemont's weather has some serious range — from a brutal 116° in September 2022 to a bone-chilling 17° in December 1932, a spread of nearly 100 degrees. The wettest single day on record dumped 5.44 inches of rain on October 24, 2021, a reminder that fall storms here can arrive fast and hit hard.
Summers in Rosemont are legitimately hot, peaking in the third week of July with average highs near 93° — not the place for heat-averse visitors. Winters are mild by most standards, with January highs averaging just 54°, and the wettest stretch of the year falls right around the holidays in late December. If you're chasing comfortable weather, aim for April through May or October, when highs land in the 70s.