Marine Heatwave off Southwest Coast of North America Continues and Cause Record Warmth for U.S. States

Climate Impact Company Daily Feature

Issued: Monday November 9, 2026

Highlight: Marine heatwave off Southwest Coast of North America continues to assist producing record warmth for U.S. states.

Fig. 1-2: Global SSTA analysis for 2026 (so far) identifying the correlation of marine heatwaves to the record warm U.S. temperature rankings.

Discussion: During 2026, marine heatwave (MHW) NEP25A persisted at record intensity off the Southwest Coast of North America (Fig. 1). NEP25A is a significant contributor to the record warm U.S. thermal pattern for all of 2026 so far (Fig. 2) especially the Southwest States. Contributions to the anomalous warmth were also made during recent months by expansion of the Kuroshio MHW and the subtropical North Atlantic MHW.

October 2026 was 4^th warmest on record and included MUCH ABOVE normal anomalies for most of the U.S. (Fig. 3). Included were many states very close to all-time-record warmth, including Missouri/Arkansas/Iowa in the Midwest States, and Idaho Interior Northwest. The Southwest U.S. Monsoon was active and produced MUCH ABOVE normal rainfall for Arizona/Nevada/Utah/Colorado (Fig. 4). Florida was also very wet. Dryness dominated the Midwest States to Mississippi.

Fig. 3: NOAA state rankings for observed temperature during October 2026.

Fig. 4: NOAA state rankings for observed precipitation during October 2026.