Summary:
- In spite of days of smoke, September was warmer than average1 across the vast majority of the western US.
- September also continued the ongoing dry conditions throughout California and the Great Basin, although western Oregon and Washington saw initial falls rains that helped with wildfires.
- The western US drought footprint is now at 90%, with nearly 55% in severe to exceptional drought. The forecast through the first half of winter is for much of the west to remain dry, with the exception of the PNW which is forecast to see a seasonal start to fall and early winter rains.
- High pressure remains in place for the first week of October, with warmer than average temperatures giving way to seasonal temperatures by the second week. Smoke will wax and wane for many, depending on the strength and direction of the wind. No precipitation is forecast through the first 10 days of the month, however a pattern shift will bring frontal systems and seasonal rain events in the latter half of the month, but these will be mostly confined to extreme Northern California, northward into the PNW.
- The forecast for October through December is largely based on the developing La Niña and a relatively warm North Pacific. As such, the PNW is anticipated to see near average to slightly warmer and wetter first half of winter, while California is expected to be warmer than average and near average to drier than average through December. The La Niña strength will likely be the most important factor to watch as winter unfolds.
