Unseasonably dry and warm conditions kick off October in the Midwest

[October 18, 2011]  CHAMPAIGN -- It was an unseasonably dry and warm start to October across the Midwest. On average, the Midwest experienced only 23 percent of its normal precipitation during the first 12 days of October, and temperatures were an average of 6 degrees above normal, according to Steve Hilberg at the Midwestern Regional Climate Center at the Illinois State Water Survey.

Up until the past few days, some locations in the western Midwest had no measurable precipitation for nearly 20 days as dry conditions extended from the end of September into early October. Kansas City, Mo., finally received measurable rainfall on Oct. 9 after 21 days without precipitation, beginning on Sept. 19. Since records began in 1934, Kansas City has experienced only seven similar dry periods lasting from late September into October, with the last occurrence happening in 1989.

Other parts of the Midwest also experienced unique dry periods during the past few weeks. Louisville, Ky., experienced 15 consecutive days without measurable precipitation from Sept. 27 to Oct. 12. This stretch of dry conditions is fairly uncommon for the subtropical climate of Louisville, which generally receives more annual precipitation than much of the Midwest.

Fifteen consecutive days without measurable precipitation has happened just 21 other times (in all months) in Louisville’s 75-year history, with 70 percent of those events occurring before 1952. The remaining 30 percent have occurred since 2001.

Across most of the Midwest, temperatures were above normal for the first 12 days of October. The largest departures from normal were found in the northwest corner of the Midwest, mainly in Minnesota, where average temperatures ranged from 10 to 16 degrees above normal during this period. Brainerd and Thief River Falls, Minn., broke their monthly October records for the highest maximum temperature, when both stations recorded 87 degrees on Oct. 5.

In addition, three other stations in Minnesota broke monthly October records for the highest minimum temperature, when International Falls and Artichoke Lake recorded a minimum temperature of 64 degrees on Oct. 7, and Gunflint Lake recorded a minimum temperature of 61 degrees on Oct. 8.

Locations in Minnesota experienced significant runs of consecutive days when temperatures reached 80 degrees or above. Starting Oct. 3, St. Cloud, Minn., experienced five consecutive days when temperatures reached 80 degrees or higher, breaking a record for the longest stretch of 80-degree temperatures ever recorded in October since records began in 1896. In Minneapolis-St. Paul, Minn., it had been 59 years since they experienced a stretch of consecutive 80-degree days similar to this year, when eight consecutive days were recorded, starting Oct. 2.

In much of the Midwest during the first week of October, the unseasonably warm days were paired with much cooler nighttime temperatures, creating large ranges in daily temperature. The daily temperature range Oct. 2-5 was 32 degrees, averaged across the Midwest. The largest daily range in temperature was 48 degrees, recorded in Hibbing, Minn., on Oct. 2 after temperatures went from a morning low of 29 degrees to a maximum temperature of 77 degrees.

[Text from file received from the Illinois State Water Survey]