U.S. and Europe HDD Forecast Update

Climate Impact Company Gas/Power Report

Issued: Friday December 26, 2025

Headline: U.S. and Europe HDD forecast update.

Discussion: Based on a consensus of all operational models, the new week is projected near normal HDD while the week ending on Jan. 8^/Jan. 15 is adjusted slightly colder to near or colder than normal (Fig. 1). The extended range projection is warmer than normal when combining the (moderately cold) ECM and (warm) CFS. The consensus of AI models is colder than normal for mid-to-late January, a colder trend. Although AI colder bias in the extended range has been favorable, the consistency of AI is not sufficient to use the projections reliably.

After a frigid start to December, the month finishes very warm. Consequently, cold U.S. population weight HDD projections for DEC-25 from earlier this month are revised sharply warmer (Fig. 2). The JAN/FEB-26 forecast remains close to the 10-year normal. The probabilistic (HDD) forecast for the U.S. indicates the risk for warmer than forecast is higher than the colder risk (Fig. 3). In Europe, colder weather arriving in late December takes the edge off the previously mild pattern for early meteorological winter while the incoming cold is sufficiently lengthy in duration to cause a colder mid-winter revision (Fig. 4).

Fig. 1-2: The U.S. 6-week gas population weight HDD forecast and the U.S. cold season monthly HDD forecast compared to the previous outlook.

Fig. 3-4: Climate Impact Company U.S. probabilistic HDD forecast for the 2025-26 cold season and the Europe selected cities cold season HDD projection.