Summary:
- September was much warmer than average[*] over the majority of the western US, especially across the inland PNW and Northern Rockies.
- Subtropical moisture brought thunderstorms to much of the West, especially California, the Southwest, and portions of the Great Basin. It was dry across the northern tier of the western states.
- March through September temperatures over the western US were 3°F warmer than average, with 64 of the 83 climate divisions seeing top ten warmest periods on record. The other 19 climate divisions, including coastal zones in central and southern California, all recorded temperatures that were in the warmest 1/3 in 131 years.
- A substantial portion of the West remains in drought with slight shifts in areas affected and the magnitude of dryness. The 90-day outlook points to southern California remaining dry, most of central to northern California staying out of drought, and improved conditions or complete removal of drought in the PNW.
- Generally cool to mild and dry over the west during the first week or so of October, then turning cooler and wetter for the rest of the month.
- 90-day seasonal outlooks heading from fall into winter often have significant week to week and month to month variation; the current forecast is no different. The overall forecast is pointing to the three-month period ending up largely warmer than average over the majority of the US; however, currently it appears that October will be mild early, cooler and wetter later, with November being relatively mild and dry, and December trending cold.
