September 2020 was warm and dry in the U.S. West, cool in the middle, and wet in the South and Southeast

October 8, 2020

According to the latest monthly summary from NOAA National Centers for Environmental Information (NCEI), the average contiguous U.S. temperature in September 2020 was 66.0°F, 1.1°F above the 20th-century average, ranking in the warmest one-third of the 126-year period of record. For the year-to-date, the contiguous U.S. temperature was 57.3°F, 2.3°F above the 20th-century average, ranking sixth warmest in the January-September record.

Map of US temperature anomaly in Sep 2020

Temperatures across the contiguous United States in September 2020 compared to the 1981-2010 average. Map from Data Snapshots on Climate.gov.

Highlights for temperature included:

  • Above- to much-above-average September temperatures were observed across much of the West, parts of the Northeast and Gulf Coast. California and Oregon ranked warmest on record for the month with Nevada and Arizona ranking second warmest,  

    • Phoenix, Arizona, broke the record for the number of days with temperatures at or above 110°F in a calendar year during August and added three more days to the record in September. The 2020 record of 53 days shatters the previous record of 33, set in 2011, 
  • Below-average temperatures were present across portions of the Plains and Deep South and in pockets scattered across the Great Lakes, Southeast and mid-Atlantic.

Meanwhile, the September precipitation total for the contiguous U.S. was 2.38 inches, 0.11 inch below average, ranking in the middle one-third of the 126-year period of record. For the year-to-date, the national precipitation total was 24.08 inches, 0.88 inch above average, also ranking in the middle one-third of the January-September record.

US map of precipitation in September 2020 as a percent of normal

U.S. precipitation as a percent of the 1981-2010 average in September 2020. Map from Data Snapshots on Climate.gov.

Highlights for precipitation included:

  • The West remained hot and dry under a relatively persistent ridge of high pressure throughout much of September, exacerbating wildfire conditions. The above-average rainfall observed across the South and Southeast were in large part due to Tropical Storm Beta and Hurricane Sally, 
  • Above-average precipitation was observed from parts of the Deep South to the mid-Atlantic and in portions of the Northwest and Midwest. Georgia had its ninth-wettest September on record, 
  • Below-average precipitation was observed from the West Coast to the northern Great Lakes and across the Northeast, and in portions of the central Gulf Coast as well as parts of the western Ohio Valley. Maine had its record-driest September, while Arizona ranked fifth driest and California sixth driest on record. In total, seven states in the Northeast, Southwest and northern Plains had their tenth driest, or drier, September.

For more details, including a summary of the number of billion-dollar disasters that have occurred so far in 2020, read the NCEI's full September 2020 climate summary.