Overview

• California’s hottest September on record is 2020 with a 74.0°F statewide average, based on NCEI data.
• Oregon’s top spot is a tie between September 2020 and September 2011 at 62.6°F on average.
• Colorado’s hottest September is 2019 at 62.9°F, with 2022 tied for third at 62.5°F.
• The rankings concentrate in the 2010s and 2020s, including California at No. 2 in 2022 and Oregon at No. 3 in 2022.
• Stacker’s state lists draw from NOAA’s National Centers for Environmental Information and align with broader warming signals, such as NOAA’s finding that July 2022 was among the hottest on record for the continental U.S.