On 21 March 2012, the 1st day of spring, the Mississippi River temperature was reported at 61º F. Generally in early spring, the river temperatures will be close to the morning 4-inch depth soil temperature. For your consideration, I have included the data in Table 1 which reflects the average last 32º F temperature in the spring based on 1971–2000 NOAA data.
Table 1 Last 32º F Temperature in the Spring for Iowa____
Franklin 1 May
Tama 28 April
Scott 22 April
Washington 19 April
Henry 16 April
Table 2 gives you a general guide for starting corn planting. Normally, it is important to know your bare 4-inch depth soil temperature in the morning and the short-term weather forecast for the next 2 to 4 days after planting. But, your soil conditions need to be right.
Table 2 Suggested Planting Date For Iowa______________
Planting Dates________ __
County Normal Earliest Practical
Franklin 25 April 20 April
Scott 20 April 15 April
Washington 15 April 10 April
Reviewing data from Illinois for the two southern most districts, and having a 3 out of 4 year probability of the last 32º F frost, April 2 and April 3 were reported as the date for that last spring frost.
Today, I would direct my planting activities to seeding alfalfa and sowing grass waterways.