Wednesday, March 28, 2012

Risk of Spring Freeze?

The Cooperative Weather Observing Station in Princeton has provided 30 year climate normals that can describe our current risk of frost injury. Princeton temperatures record a final freeze of 28 degrees Fahrenheit or less to occur during March 21-31, on average. The strength of this prediction is lessened due to the stations in Evansville and Vincennes both recording final hard freeze dates in the April 1-10 range. The last average date of a 32 degree Fahrenheit freeze is more uniform across the region, with Mt. Vernon, Evansville, and Princeton all recording their average final freeze during April 1-10. According to this data, our likelihood of damaging frost decreases greatly after April 10.

The earliest date of the final spring freeze in this area has been prior to March 10 at times over the last 30 years. The possibility that this year will have the distinction of a final spring freeze date of March 10 exists. The National Climactic Data Center compiles information and releases probability maps of spring freezes. The time period after which we have a 10% or less chance of seeing 28 degrees is April 15. For a 10% or less chance of seeing 32 degrees, that date looks closer to May 1. If we should receive a frost or freeze in the next couple of weeks, the time period over which we experience the cold temperatures will also play a role of high importance.

Freezing temperatures experienced briefly and without frost will do much less damage than a hard frost with temperatures of less than 28 degrees Fahrenheit extended over several hours. At this point, risks must be evaluated against rewards. The potential for a longer growing season may benefit your garden or fields if you plant soon (or have already planted), but the potential for a freeze or frost damage must also be considered.