Dry Growing Season 2008 (updated October 2, 2008)
Abrupt changes in precipitation patterns over time are common in Minnesota. This was the case during the 2008 growing season. A lengthy stretch of very dry weather arrived immediately on the heels of an extremely wet first half of June.
For the fifteen-week period during the last two weeks of June and into late September, many Minnesota communities received less than eight inches of rainfall. This came at a time of year when rainfall rates average roughly one inch per week. Thus, rainfall deficits over the fifteen-week dry spell topped five inches in many areas. Described another way, fifteen-week rainfall totals in some locales were less than 60 percent of normal for the period. When compared with the same fifteen-week time span in previous years, 2008 growing season rainfall ranked below the 5th percentile (one year in twenty) in many southern Minnesota communities (see maps below). In a few south-central Minnesota locations, precipitation totals for the period June 17 through September 29 were at or near the all-time historical minimum for that fifteen-week period.
Temperatures over the fifteen-week period were very close to historical averages. Days with temperatures in the 90 were relatively rare. This kept evaporative demand near seasonal norms and mitigated the situation somewhat.
As of September 30, the U.S. Drought Monitor rated much of Minnesota in the D0 - Abnormally Dry category or worse (see map at right). Significant portions of the state were placed in the D1 - Moderate Drought classification. A small area of sorth central Minnesota was designated as undergoing a D2 - Severe Drought.
Previous week's weather:
The weekly rainfall map for September 23 through September 29 showed that significant rain fell in the northeast quandrant of Minnesota. Many communities reported two or more inches of precipitation for the week. While seasonal precipitation deficits are still substantial in these areas, the rains were particularly welcome and mitigated the drought situation somewhat. Temperatures for the week were quite warm, averaging six to ten degrees above the seasonal normal.
- Agriculture - The Agricultural Statistics Service reported that as of September 26, topsoil moisture across 28 percent of Minnesota's landscape was "Short" or "Very Short". In the September 29 Crop Progress and Condition Report, 65 percent of corn and 60 percent of soybeans were rated in good or excellent condition.
- Stream flow - Late September stream discharge in Minnesota rivers and streams was highly variable across the state. Some Minnesota streams reported flows that were below the 25th percentile in the historical distribution for the final week of September. By contrast, the Red River and many of its tributaries reported above-median flows in response to heavy rains that fell in August and early September.
- Wildfire Danger - The Department of Natural Resources - Division of Forestry classified late September wildfire danger as Low throughout Minnesota.