The temperature forecast bias among two leading “weeklies” forecast models is clearly too hot in the 16-30-day period across the West and Central U.S. The explanation for the warm (ECM) bias is presence of an unusually strong summertime polar vortex over Greenland with a southward extending upper trough occasionally visiting the West U.S.

The 12-week Evaporative Drought Demand Index (EDDI) reveals U.S. areas most susceptible to fire risk for late meteorological summer/early autumn. The highest alert, ED3/ED4 is spread across central and southern California, much of the Great Basin, and Arizona.

Searing heat dominated East China and Japan beneath intense subtropical high pressure during July 2025. The latest week 2-4 outlook regenerates additional late summer excessive heat for the region.

The 12Z GFS is hot in the Southwest during the 6-10-day period and trending warmer from the eastern Canadian Prairies to Quebec. In the 11-15-day period, the 12Z GFS explodes hotter into the Northeast U.S. causing 106 CDD for Aug. 8-14 which would easily exceed the current week.