Birds of the St. Croix River Valley: Minnesota and Wisconsin

Climate

The Valley has a temperate, continental climate that is characterized by extreme seasonal variability. Mean monthly air temperatures are -12 to -9 °C in January and 20 to 22 °C in July. The average growing season ranges from 100 days in the north (Burnett and Pine counties) to over 120 days in the south (St. Croix and Washington counties). The ground is frozen usually from late November through mid-April and frost depths range from 66 to 86 cm.

Mean annual precipitation is 74.4 cm (Young and Hindall 1973). The range in yearly precipitation is about 71.1 cm at St. Croix Beach, Washington County, to nearly 78.7 cm at Grantsburg, Burnett County (Lindholm et al. 1974). Periods of prolonged drought are highly infrequent. February is usually the driest month (<2.5 cm) and June the wettest (12.2 cm). Annual evapotranspiration from the St. Croix watershed is 59.4 cm (Lindholm et al. 1974). During July and August, when temperatures are highest and plant moisture demands are greatest, evapotranspiration often exceeds precipitation.

Previous Section -- Abstract
Return to Contents
Next Section -- Geology