A concentrated area of regenerating and slow-moving heavy thunderstorms in central Minnesota produced large hail and the state's most extreme rainfall to date from the evening of Thursday June 23 into the morning of June 24, 2022.
The storms formed along an axis of enhanced moisture and lift that had developed throughout the day, as strong heating spread over much of the state. Although other isolated storms formed during the day and into the night, the main event affected a relatively small pocket of Minnesota, from the western Brainerd Lakes area, down to around Elk River, and eastward to Mora and Taylors Falls.
Most of the large hail was concentrated in Crow Wing, Aitkin, and St. Louis counties. Areas near Brainerd, in particular, endured quite a barrage of hail, with half dollar, ping pong ball, golf ball-sized, and even larger hail hitting many places multiple times over a three-hour period. Large hail also fell near Aitkin, Big Sandy Lake, and later near St. Cloud. Just after sunrise on Friday, separate intense storms developed in Otter Tail County, producing tennis ball-sized hail in Battle Lake and baseball-sized hail near Ottertail just before 7 AM.
The storms built southward slowly, with new cells forming on the west side of the complex and moving over previously-hit areas. This led to prolonged and recurrent episodes of intense rainfall, with rain totals well in excess of three inches northwest of Little Falls, and also in St. Cloud and neighboring communities. A small area near Randall and Cushing received extraordinary rainfall totals, leading the closure of US Highway 10 in both directions because of flooding in the area.
The highest rainfall total received came from Soil & Water Conservation District rain gauge reader near Cushing, and will be marked as "11 inches," because the observer had noted that the rain had reached the gauge's 11-inch capacity and that additional rain was simply pouring out of it. It is not known how much more rain actually fell. Another observer from the same network in Randall recorded 7.40 inches.
In the St. Cloud area, a CoCoRaHS observer in Sartell reported 7.11 inches, with 5.93 inches reported northwest of town, 5.50 and 4.86 inches in Sauk Rapids, 4.61 inches reported in St. Joseph, and 4.20 inches reported in St. Cloud proper. Through 9 AM, the St. Cloud airport, which is several miles east of the city, recorded 3.81 inches.
Of note: These storms produced extreme-intensity rains, but over an area too small to qualify it as a "mega-rain" event. That said, double-digit rainfall totals are highly unusual in Minnesota, and are not reported in most years. For a given location in this part of Minnesota, the probability of receiving 10 inches of rain or more in 24 hours is less than one tenth of one percent, meaning the rains near Cushing and Randall exceeded the "1000-year" rainfall threshold. In this region, a 200-year rain of 24-hour duration is just over 7 inches, a 100-year rain is around 6.25 inches, 50-year rains are about 5.5 inches, and a 25-year event would be 4.75 inches. Thus, in a small part of central Minnesota, these were truly extreme rains.
June 30, 2022