Intriguing U.S. HDD Forecasts for January 2-8

Climate Impact Company U.S. Medium Range Report

Issued: Wednesday December 24, 2025

Highlight: Cold 6-10-day forecast increases aerial coverage. Extended range is intriguing.

Charts of the day: Jan. 2-8 low confidence HDD forecast.

Discussion: Utilizing all operational models, forecasts are agreeable to the decelerating warm pattern to near the 10-year normal for next week. In the Jan. 2-8 period, forecast models vary widely from a milder national scenario (GFS ENS/GFS) to much colder than normal (CMC ENS/ECM). The just released GFS was near the overnight consensus.

Medium-range 6-10 Day Forecast Valid December 29, 2025-January 2, 2026 (ECM ENS left and 24-hour change right)

Discussion: West/Central Canada cold spills into the East/Southeast U.S. driven by a fortified -NAO circulation. The air mass features minimal arctic air although locally frigid temperatures are possible across established snow cover. The 24-hour change indicates widening aerial coverage of the cold.

Medium-range 11-15 Day Forecast Valid January 3-7, 2026 (ECM ENS left and 24-hour change right)

Discussion: In the 11-15-day period, a changeable pattern averaging colder than normal lingers across the Great Lakes to the Northeast U.S. while south of that arc the weather remains mild. The West is losing the mild tendency.

U.S. Medium-range Precipitation Forecast

Discussion: Atmospheric river storm track shifts south and into Mexico to the Southwest U.S. while Canada is snowy in the 6-10-day period. Most of the West is stormy in the 11-15-day period with rain likely across the Southeast.

Days 16-20 Extended range Temperature Forecast valid January 8-12, 2026

Discussion: The most likely scenario (45% risk) is indicated by the ECM maintaining Northern U.S. cold risk while the remainder of the U.S. is warm. There is some risk that each coastal location could be colder.