NATIONAL WEATHER SUMMARY

SEPTEMBER 2025

Aug. 31-Sep. 6: Mostly dry weather across the remainder of the country—including northern sections of the Rockies and High Plains, parts of the Midwest, and much of the lower Southeast.

Weekly temperatures averaged 5 to 15°F above normal in the Northwest— excluding coastal locations— extending as far east as western Montana. In contrast, chilly conditions covered much of the central and eastern U.S., with temperatures averaging as much as 10°F below normal from the central Plains into the Midwest. Temperatures remained below 80°F all week in the Midwest as far south as Iowa and eastern Nebraska. Frost and light freezes affected parts of the northern Plains and upper Midwest, although temperatures were not low enough to significantly threaten immature summer crops, such as corn and soybeans. On the northern Plains, small grains—including barley and spring wheat—were already mature, with harvest nearing completion in many areas. A late-summer Northwestern heat wave lingered into early September. Spokane, WA, registered daily record highs (99, 99, and 98°F) on each of the first 3 days of the month. Omak, WA, also tallied a trio of daily-record highs, noting 101, 104, and 102°F from September 2-4. Elsewhere in the West, daily record highs included 105°F (on September 1) in Hanford, WA; 102°F (on September 1) in Lewiston, ID; and 99°F (on September 3) in Wenatchee, WA. Meanwhile, east of the Rockies, progressively cooler air surged southward. September opened with daily-record lows in mid-Atlantic locations such as Charlottesville, VA (49°F), and Baltimore, MD (52°F). A day later, Macon, GA (57°F) tied a daily record for September 2. Late in the week, a record-breaking chill enveloped the northern Plains and upper Midwest. By September 4, Sisseton, SD, collected a daily record low of 36°F. Two days later, September 6 featured a broad array of daily-record lows, from 30°F in Dickinson, ND, to 38°F in Sioux City, IA. Rapid City, SD, closed the week on September 5-6 with a pair of daily record lows (35 and 33°F, respectively). Light freezes (and daily-record lows) affected several locations on September 6, when readings dipped to 29°F in Hibbing, MN; 31°F in Sheridan, WY; and 32°F in Livingston, MT.

7-16: Florida’s peninsula experienced frequent showers delivering more than 4 inches of rain in some east coastal locations. As the week progressed, interaction between cold fronts and the North American monsoon circulation led to several areas of unsettled weather. Namely, scattered showers stretched from Oregon and northern California into the upper Great Lakes region, with that area intersecting a ribbon of rain extending northward from southern sections of the Rockies and High Plains. Rain also fell across southern Texas. Mostly dry weather prevailed across remainder of the country, including much of Washington State, along with central and southern California and the Great Basin.

cool conditions shifted eastward and gradually eased. Still, weekly temperatures averaged 5 to 10°F below normal in many locations across eastern one-third of the U.S. In contrast, consistent warmth in the North extended from central Washington to the northern Plains, where temperatures averaged as much as 5 to 10°F above normal. Late in the week, warmth advanced across the remainder of the Plains and into the upper Midwest. Early in the week, a significant chill prevailed across much of the eastern half of the U.S. September 7 featured daily-record lows in dozens of Midwestern locations, including Grand Forks, ND (32°F); Sisseton, SD (33°F); Sioux City, IA (36°F); and Flint, MI (36°F). Hibbing, MN, reported three consecutive freezes from September 6-8, including a daily-record low of 29°F on the final day of the cool spell. Locations such as Flint, MI (36 and 37°F), and Fort Wayne, IN (39 and 36°F) opened the week on September 7-8 with consecutive daily-record lows. Record-setting lows for September 9 were set as far south as Athens, GA (54°F), and Greenville-Spartanburg, SC (52°F). Days later, however, warmth spread eastward from the Northwest. By September 11, Rapid City, SD, registered a daily-record high of 100°F. On September 13, Midwestern daily-record highs surged to 97°F in Vichy-Rolla, MO, and 96°F in Des Moines, IA. Late-week heat spread as far east as the lower Mississippi Valley, where Greenwood, MS, collected a record-setting high (98°F) for September 13.

14-20:  Dry weather also dominated the Deep South—excluding southern Florida and the southern tip of Texas. Along the middle Atlantic Coast, a non-tropical storm system interrupted an otherwise dry weather pattern. Farther west, out-of-season showers—associated with moisture stripped from the remnants of eastern Pacific Tropical Storm Mario—fell in central and southern California and parts of the Southwest. Isolated showers dotted the Northwest, where more rain will be needed for the establishment of fall-sown crops, while mostly dry weather prevailed from northern California to the Intermountain West.

Late-season warmth dominated the eastern half of the U.S., except along and near the Atlantic Coast. Warm weather also covered the nation’s northern tier, extending as far east as the Great Lakes States. Weekly temperatures averaged 5 to 10°F above normal in much of the Mississippi Valley, extending to other regions. Notably, readings also averaged at least 5°F above normal from central and eastern Washington into the upper Midwest. In contrast, temperatures averaged as much as 5°F below normal in the middle and southern Atlantic States. Cooler-than-normal conditions also prevailed in the central Rockies, but the remainder of the western U.S. experienced near- or above-normal temperatures. Despite widespread and sustained warmth in the Mississippi Valley and neighboring areas, only scattered records were set. In Missouri, however, daily-record highs included 96°F (on September 14 and 18) in Cape Girardeau and 95°F (on September 16) in Springfield. From September 11-18, high temperatures ranged from 92 to 96°F each day in Cape Girardeau and 91 to 95°F in Springfield. There was also a notable warm spell in the Pacific Coast States, where record setting highs for September 16 rose to 96°F in Roseburg, OR, and 91°F in Seattle, WA. In California, Livermore noted a daily-record high of 99°F on September 17.

Late in the week, heat shifted into parts of the South and East, where selected daily record highs included 98°F (on September 18) in Jackson, TN, and 91°F (on September 20) in Parkersburg, WV. A few days earlier, when cool air had lingered in the Atlantic Coast States, record-setting lows in Florida for September 15 had included 56°F in Tallahassee and 60°F in Jacksonville.

21-27: warmth covering much of the country, weekly temperatures averaged 5 to 10°F above normal from the northern Plains into the Great Lakes States. Readings also averaged at least 5°F above normal in portions of Texas and northern and central California. In contrast, near-normal temperatures were observed in a few areas, including the central Rockies, southern Florida, and the Pacific Northwest. As the week began, hot weather in Florida led to daily record-tying highs for September 21 in Tampa (95°F) and Naples (94°F). Late-season heat also developed across Texas, where daily-record highs for September 22 soared to 100°F in Midland and 99°F in Lubbock. On September 23, triple-digit, daily-record highs in Texas included 102°F in Abilene and 101°F in Austin (Camp Mabry). With mid-week heat locked in across much of the Southeast, record-setting highs for September 24 included 95°F in Gainesville, FL, and 94°F in Florence, SC. Another daily record high (96°F) occurred in Florence on September 25. Heat also briefly affected the Northwest, where Medford, OR, tied a daily record high (99°F) for September 24. Late in the week, late-season warmth expanded into other areas, including much of the North and Midwest. On September 26, Waterloo, IA, collected a daily record high of 89°F. 

 

Jim G. Munley, jr.
http://www.jimmunleywx.com