Climbing Heating Degree Days in U.S. as December Arrives
11/19/2025, 4:48 am EST
Climate Impact Company Early U.S. Notes
Issued: Thursday November 20, 2025
Highlight: Following 2 issues…Developing cold pattern and Texas rains.
*New NOAA/CPC long-lead climate forecasts/drought outlook issued today.
**5-day forecasts extended to 6 days to cover Thanksgiving travel issued afternoon.
Fig. 1: The U.S. gas population weight HDD forecast based on all operational models through Dec. 4th and estimated HDD combining CFS/ECM and AI models for weeks 4-6 ahead.
Discussion: The U.S. gas population weight HDD forecast through December 4th is similar with yesterday’s outlook featuring low heating demand through Thanksgiving Day increasing to higher than normal in early December (Fig. 1). The CFS/ECM consensus indicates near or colder than the 30-year normal for weeks 4-6 ahead, a colder change. AI models also shift colder with above normal U.S. heating demand indicated for most of December. The “most likely” upper air pattern in 15 days according to the mega-cluster ensemble is a prohibitive polar vortex across Hudson Bay (Fig. 2). The “caveat” forecast suggests any extension of the cold trough is into the Central U.S. (Fig. 3). On day-15, snow cover is deep across Canada and capable of sustaining very cold air (Fig. 4). However, in the U.S., snow cover is below normal except for the far northern states (and Continental Divide). The lack of snow biases the U.S. less cold. In the stratosphere, warming across Canada is intensifying particularly in the extended range at day-15 (Fig. 5). Stratospheric warming supports the tropospheric polar vortex pattern. The extended range diagnostics are supportive of Northern U.S. cold well into December.
Fig. 2-5: ECM ENS 11-15-day and day-15 10 MB temperature anomalies.
A second issue is Texas rainstorms ahead. The wet weather forecast is a surprise given the strengthening La Nina climate and usual relationship that La Nina has on Texas climate patterns promoting dryness and drought. Excessive rainfall with flood risk is forecast for today southwest of San Antonio and in Arkansas. Excessive rainfall with flood risk returns to Texas and the southeast Great Plains SUN/MON. The NBM 10-day rainfall forecast indicates 5-7 in. of rain just north of Dallas (Fig. 6).
Fig. 6: NBM 10-day precipitation amount forecast for the East U.S.