Overview

• Oregon’s coldest September was in 1895 with a 51.5°F statewide average, a 62.4°F monthly high, a 40.6°F low, and 2.33 inches of precipitation.
• California’s coldest September was in 1986 with a 63.5°F statewide average, a 75.8°F monthly high, a 51.1°F low, and 1.4 inches of precipitation.
• Colorado’s coldest September was in 1912 with a 51.0°F statewide average, a 64.8°F monthly high, a 37.1°F low, and 1.32 inches of precipitation.
• Rankings rely on the lowest average statewide temperature for September, and each entry lists the average, monthly high and low, and total precipitation.
• The compilations, drawn from NCEI records, were published on Sept. 30, 2025 by local outlets KTVZ (Oregon), KYMA (California), and KRDO (Colorado), and include multiple ties across decades.