Thunderstorms and Heavy Rain, August 6-8, 2021

Multiple rounds of thunderstorms and heavy rain helped parts of southern Minnesota avoid sliding deeper into drought conditions.

A large shield of rain with embedded thunderstorms came out of South Dakota late Friday evening and began affecting far western Minnesota before midnight. In the early morning hours on Saturday, several different bands of thunderstorms advanced across the southern half or so of the state. Atmospheric conditions promoted slow-moving and regenerating thunderstorms, which led to some areas receiving downpours lasting an hour or more. A typical thunderstorm downpour in Minnesota peaks for 15-20 minutes.

The morning activity left behind a variety of temperature boundaries and multi-county-sized circulations that meandered across the region during Saturday, triggering more thunderstorm development in southeastern Minnesota, and a spiraling complex of intense storms that trudged into far western Minnesota overnight. Additional thunderstorms blossomed over southern Minnesota again early Sunday morning.

The on-and-off scattered thunderstorm activity produced an uneven and erratic pattern of precipitation totals, with one prong of higher totals extending from Canby and Granite Falls through the southern Twin Cities area, and another covering extreme southeastern Minnesota. The highest precipitation totals for the event were reported at National Weather Service cooperative observing sites in far southeastern Minnesota, including 6.96 inches near La Crescent, 5.27 inches near Hokah, 4.30 inches at Caledonia, and 4.11 inches at the Winona Dam. Totals of 2-3 inches were reported by observers along the western Minnesota River near Granite Falls and Montevideo, as well as in parts of the central, southern, and eastern Twin Cities area. 

This precipitation event occurred in the midst of a major, escalating drought episode. During the summer, about an inch of rain per week is required to keep precipitation deficits from growing. Thus, areas that received an inch or more effectively held the drought steady, at least temporarily. Areas that received over two inches may have seen small short-term improvements in drought conditions. Unfortunately, approximately 50% of the state did not receive even a half-inch of rain over the week of August 4-10, and large pockets of northwestern and far northeastern Minnesota received a tenth of an inch or less. Suffice it to say, these weekly precipitation shortfalls did not help the drought situation.

Below are rainfall totals reported from Friday August 6 to Monday August 9, 2021.   

Station	Network	Total (in.)
LA CRESCENT DAM 7	COOP	6.96
HOKAH 4NW	COOP	5.27
CALEDONIA	COOP	4.3
WINONA DAM 5 A	COOP	4.11
CLARKFIELD 4.7 NE	CoCoRaHS	4.05
MABEL	COOP	3.25
THEILMAN 1SSW	COOP	3.08
WOODBURY 1.8 NW	CoCoRaHS	3.06
NEW PRAGUE 0.9 NNE	CoCoRaHS	3.04
WABASHA	COOP	2.89
GRANITE FALLS	COOP	2.86
WOODBURY 0.3 WNW	CoCoRaHS	2.84
MONTEVIDEO 4.0 S	CoCoRaHS	2.82
WOODBURY 1.7 N	CoCoRaHS	2.73
MINNESOTA CITY DAM 5	COOP	2.71
MAPLEWOOD 5.6 SSE	CoCoRaHS	2.71
BIRD ISLAND 7SSE	COOP	2.61
MAPLEWOOD 4.3 SSE	CoCoRaHS	2.61
WOODBURY 0.3 NNW	CoCoRaHS	2.58
LAKELAND 1.8 S	CoCoRaHS	2.51
BROWNTON 0.2 SSE	CoCoRaHS	2.51
BIRD ISLAND 0.3 SW	CoCoRaHS	2.48
BIRD ISLAND 7.2 SSE	CoCoRaHS	2.46
BROWNTON WWTP	COOP	2.38
NEW PRAGUE 1.0 NNW	CoCoRaHS	2.29
MONTEVIDEO 0.4 SSW	CoCoRaHS	2.25
RENVILLE 3.4 N	CoCoRaHS	2.25
ALTURA 5W	COOP	2.24
WILD RIVER STATE PARK	COOP	2.18
NEW PRAGUE 0.5 SE	CoCoRaHS	2.16
MINNEAPOLIS-ST. PAUL INTERNATIONAL AIRPORT	WBAN	2.09
Minneapolis-St Paul Area	ThreadEx	2.09
RAYMOND 4.7 WSW	CoCoRaHS	2.04
UNIVERSITY OF MN ST. PAUL	COOP	2.01
LAKE CITY	COOP	2
RENVILLE 3.7 ENE	CoCoRaHS	2
DAWSON	WBAN	1.93
WHEATON	COOP	1.92
AFTON 1.6 E	CoCoRaHS	1.92
ZUMBROTA	COOP	1.9
NEW PRAGUE 1.0 S	CoCoRaHS	1.83
HASTINGS DAM 2	COOP	1.8
CHANHASSEN WSFO	COOP	1.8
OAKDALE 2.4 SSE	CoCoRaHS	1.77
BROWNS VALLEY	COOP	1.76
VADNAIS LAKE	COOP	1.75
IVANHOE 5.7 E	CoCoRaHS	1.74
STILLWATER 2SW	COOP	1.68
WASECA 6.0 N	CoCoRaHS	1.6
TWO HARBORS 9.7 NNE	CoCoRaHS	1.58
COTTAGE GROVE 1.7 NW	CoCoRaHS	1.54
GLENCOE 0.3 WSW	CoCoRaHS	1.51
LOWER ST. ANTHONY FALLS	COOP	1.5
Rochester Area	ThreadEx	1.48
ROCHESTER INTERNATIONAL AIRPORT	WBAN	1.48
SOUTH SAINT PAUL 1.1 W	CoCoRaHS	1.48
ORTONVILLE 1N	COOP	1.47
BIRD ISLAND 9.0 NNE	CoCoRaHS	1.46
MINNEAPOLIS 4.1 SSW	CoCoRaHS	1.46
REDWOOD FALLS	COOP	1.44
WASECA 2.0 N	CoCoRaHS	1.44
ANOKA 6.5 N	CoCoRaHS	1.43
HILLS 0.2 NW	CoCoRaHS	1.42
WATSON 1NE	COOP	1.4
SAINT PAUL 5.1 SW	CoCoRaHS	1.4
ARTICHOKE LAKE 1 E	COOP	1.37
JORDAN 4.2 SSE	CoCoRaHS	1.37
LONSDALE 2.8 NNE	CoCoRaHS	1.35
CANBY	COOP	1.34
PRESTON	COOP	1.34
GREEN ISLE 1.7 WNW	CoCoRaHS	1.33
HOLYOKE 2.7 ENE	CoCoRaHS	1.33
REDWOOD FALLS 0.6 NE	CoCoRaHS	1.33
ST PAUL PARK 0.6 NNE	CoCoRaHS	1.32
MINNEAPOLIS 3.3 S	CoCoRaHS	1.31
PINE CITY 1.8 ENE	CoCoRaHS	1.3
MONTEVIDEO 2.2 N	CoCoRaHS	1.3
REDWOOD FALLS MUNICIPAL AIRPORT	WBAN	1.29
EDGERTON 0.2 WSW	CoCoRaHS	1.28
MINNEAPOLIS 4.9 SE	CoCoRaHS	1.28
MINNEAPOLIS 3.8 SSW	CoCoRaHS	1.26
EDEN PRAIRIE 2.5 WSW	CoCoRaHS	1.23
FAIRFAX 4.9 SSE	CoCoRaHS	1.23
NORTHFIELD 2.4 NE	CoCoRaHS	1.2
SACRED HEART 5.8 S	CoCoRaHS	1.2
EXCELSIOR 1.8 W	CoCoRaHS	1.19
RED WING DAM 3	COOP	1.18
GLENCOE 3.2 NNW	CoCoRaHS	1.17
WORTHINGTON 1.9 SW	CoCoRaHS	1.14
CHASKA 1.1 WSW	CoCoRaHS	1.13
EDEN PRAIRIE 3.1 ESE	CoCoRaHS	1.12
NORWOOD YOUNG AMERICA 0.9 ENE	CoCoRaHS	1.11
RICE	COOP	1.09
CENTER CITY 0.8 WSW	CoCoRaHS	1.08
ANDOVER 1N	COOP	1.07
EDEN PRAIRIE 3.3 WSW	CoCoRaHS	1.07
CARVER 0.7 W	CoCoRaHS	1.06
OAKDALE 0.4 S	CoCoRaHS	1.06
MINNEAPOLIS FLYING CLOUD AIRPORT	WBAN	1.05
PIPESTONE	COOP	1.05
CHANHASSEN 3.4 NW	CoCoRaHS	1.05
INTERNATIONAL FALLS 7.7 S	CoCoRaHS	1.05
PLATO 0.3 ENE	CoCoRaHS	1.05
SAINT PAUL 1.7 N	CoCoRaHS	1.04
ST. PETER	COOP	1.03
KABETOGAMA	COOP	1.03
JORDAN 1SSW	COOP	1.02
WASECA 1.6 SSE	CoCoRaHS	1.02
CHASKA 0.6 E	CoCoRaHS	1.02
TAYLORS FALLS 6.1 NW	CoCoRaHS	1.01
NEW PRAGUE 1.1 ESE	CoCoRaHS	1

Last modified August 11, 2021.