California Observes Hottest July on Record

Discussion: The hottest July on record was observed in California (Fig. 1). An upper-level ridge in-between a low-pressure area in the central Great Plains and south of Alaska enhanced by the influence of a marine heat wave shifting into the northeast Pacific were catalysts to the record heat. Additionally, New Hampshire observed the hottest July on record thanks to another buoyant high-pressure ridge located over Nova Scotia. Nationally, the U.S. observed the 11^th hottest July in the 130-year climatology. The entire Northeast Corridor and West U.S. observed a top 10 hottest mid-summer. The Midwest States were temperate to cooler than normal.

Nationally, July 2024 was a moderately wet month ranking 30^th wettest in the 130-year climatology. Wet regions were the Midwest where Illinois was 7^th wettest on record and the Southeast States where North Carolina was 8^th wettest on record (Fig. 2). Despite the wet month in North Carolina, nearby West Virginia was 8^th driest on record. The East-central U.S. to the northwest Gulf of Mexico Coast were each wetter than normal. Almost the entire western 40% of the U.S. was drier than normal although without extremes.

The May/June/July 2024 seasonal temperature rank was 5^th warmest on record inspired by record warmth in New England, New York, and Pennsylvania plus Florida (Fig. 3). Much of the West, South, and Mid-Atlantic U.S. observed top 5 warm 90-day periods for late spring to mid-summer. Only the northwest Great Plains were temperate.

Precipitation was near record amount across the Upper Midwest during May/June/July 2024 (Fig. 4). Wisconsin observed their 2^nd wettest July on record. Most of the eastern half of the U.S. was wetter than normal except for a small dry region involving Ohio, Pennsylvania, Maryland, Delaware, New Jersey, and West Virginia. Much of the West was drier than normal especially Nevada (6th driest).

Fig. 1: The NOAA state rankings for July 2024 of anomalous temperature.

Fig. 2: The NOAA state rankings for July 2024 of anomalous precipitation.

Fig. 3: The NOAA state rankings for May/June/July 2024 of anomalous temperature.

Fig. 4: The NOAA state rankings for May/June/July 2024 of anomalous precipitation.