Southeast U.S. Becoming a Warm-to-Hot Air Mass Source Region

Climate Impact Company Early U.S. Notes

Issued: Tuesday April 7, 2026

Highlight: SERC becoming a concern area as a warm-to-hot air source region as the warm season approaches.

Climate: Washington Post “strongest El Nino on record” ahead for 2026 article yesterday. Is that true? Climate Impact Company updates the 2026-27 ENSO Outlook later today.

Fig. 1: Daily soil moisture rankings implicate the Southeast U.S. as the driest zone with highest susceptibility to extreme heat as the warm season approaches.

Discussion: The southeast quadrant of the U.S. daily soil moisture rankings observations reveals historically dry conditions (Fig. 1). As the warm season approaches, large regions of dry soil have increasing risk of extreme heat which can worsen drought. The 15-day SERC population weight daily average temperature forecast reveals evolving important heat for the medium range featuring risk of 90F (Fig. 2). Briefly, the warm air source region extends northward into PJM-East mid-April (Fig. 3). The GFS ENS risk of >90F temperature threshold begins to emerge later this week and is evident during the 6-10-day period in the Southeast, Texas, and Desert Southwest (Fig. 4). Aerial coverage of >90F risk increases substantially in the 11-15-day period (Fig, 5). The U.S. gas population weight HDD forecast reveals a less warm change for next week (Fig. 6).

Fig. 2: The 15-day population weight daily average temperature 15-day forecast for SERC.

Fig. 3: The 15-day population weight daily average temperature 15-day forecast for PJM-East.

Fig. 4-5: The GFS ENS 6-10-day/11-15-day risk of >90F maximum temperatures.

Fig. 6: U.S. gas population weight HDD forecasts utilizing all models, their consensus, and comparison with yesterday’s forecast and the 10-year/30-year climatology.