5th Warmest December on Record in U.S.

Climate Impact Company Midday Update

Issued: Tuesday January 13, 2026

Highlight: DEC-25 U.S. climate review. 12Z GFS trends (arctic) cold extended range.

Fig. 1: The NOAA/CPC U.S. state temperature rankings for December 2025.

Discussion: DEC-25 was the 5^th warmest early winter in the 131-year historical record (Fig. 1). Almost the entire West observed the warmest December on record while the Northeast was seasonably cold. The U.S. precipitation pattern during DEC-25 ranked 37^th driest on record featuring the driest December on record in Oklahoma with near record dryness for surrounding states, a classic La Nina signature (Fig. 2). Meanwhile a wet La Nina bias was exceptional across the Northwest States.

The 12Z GFS likes the morning forecast philosophy of an aggressive -AO pattern causing Eurasia chill to shift cross-polar and into North America. Consequently, a cold 6-10-day forecast shifts colder in 11-15 days and features arctic air (Fig. 3-4).

Fig. 2: The NOAA/CPC U.S. state precipitation rankings for December 2025.

Fig. 3-4: The 12Z GFS medium range temperature anomaly forecast.

Table 1: The midday 12Z GFS U.S. gas population weight HDD projections into later January.