September 8-14, 2024

Temperature

There was a stark contrast in average temperature departures across the region this week. Since the period started cool in the wake of a cold front, many of the southern and western areas had not yet seen temperatures recover to September normals. In much of the Upper Midwest, average temperatures were 4-8°F above normal, and even higher in northern Minnesota (Figure 1). In the lower Midwest, specifically southern Illinois, southern Indiana, southern Ohio, Missouri and Kentucky, temperatures were 3-5°F below normal. They were near normal along the I-80 corridor.

Average minimum temperatures were even more anomalous, especially early in the period. In Minnesota they were as much as 8-9°F above normal, while in the Ohio Valley they were as much as 8°F below normal (Figure 2). A temperature of 39°F was recorded in Terre Haute, Indiana on September 8. This was both a daily record low temperature and the earliest such temperature in meteorological fall at that station. In Vichy, Missouri, a station observed a temperature of 42°f on September 8, the earliest that station recorded a temperature that low in meteorological Fall.

Average maximum temperatures varied for the same aforementioned reasons. In northern Minnesota, they were over 10°F above normal, and much of the Upper Midwest was quite a bit above normal (Figure 3). The I-80 corridor, which was 2-4°F above normal, and in southern Missouri they were actually 2-4°F below normal.

Precipitation/Drought

There was just about no precipitation for most of the region this week. High pressure dominated, keeping the remnants of Hurricane Francine south of most of the region, though parts of the mid-Mississippi River Basin did get in on some decent rainfall. In fact, the Missouri Bootheel, far southern Illinois, and far western Kentucky observed 100 percent of normal precipitation thanks to Francine (Figure 4). Paducah, Kentucky, received greater than 0.75 inches of precipitation two consecutive days, August 12-13, for the first time in September since 2006.

Elsewhere, there was generally zero percent of normal precipitation. Some spots have received no measurable precipitation since August. A station in Park Rapids, Minnesota went 13 days, through September 13, with no measurable precipitation, which was the driest stretch of September weather for that station since 2011. Superior, Wisconsin had seen no measurable precipitation since August 30, and as of September 14 had still not recorded more than trace precipitation, making it tied for the 4th longest stretch of no measurable precipitation in September.

As a result of the drier pattern, drought only expanded. By September 10, at least 65 percent of the Midwest was reporting D0 (abnormally dry) conditions (Figure 5). Another 22 percent were reporting D1 conditions (moderate drought), double the percentage the week before. D4 conditions (exceptional drought) expanded slightly in Ohio, now covering 0.7 percent of the state.