Under the Köppen climate classification, Hermosillo features a hot desert climate (BWh). Temperatures can range from as low as freezing in December and January to 48 °C (118.4 °F) in June and July. Rain falls mostly between July and September, with annual precipitation between 75 and 300 millimetres (3.0 and 11.8 in). Most of the vegetation here consists of mesquite trees as well as trees such as the desert ironwood, palo verde and the huisache. Desert animals such as the desert tortoise, rattlesnakes, bighorn sheep and lynx are the most notable species. Populations of feral red-masked parakeets and monk parakeets are a local sightseeing attraction here.
Hermosillo’s all-time weather record for high temperature is 49.5 °C (121.1 °F), which was achieved in June 2014. In recent years, the lowest temperature was −4 °C (24.8 °F), in December.