When Will the First Frost Arrive?

While global warming will probably have a large effect on Illinois by 2090, its effects from year to year are tiny or negligible. We may think our winters are getting consistently warmer, but they aren't. While the warm winter of 2011-12 had a low of only +5º F, the winter of 1959-60 had a low of even less--+6º F. It's close to impossible to predict our winters right now because of the multitude of different factors.

What about that first frost date--temperature below 32º? It can hit as early as Sept. 22, as it did in 1995. Or it can be as late as Nov. 24, as it was in 1931. How can you plan? The latest Farmers' Almanac gives Oct. 24 as the average first frost date for our area but fails to say how many years have been tallied. For the years 1981-2010 the median date is Oct. 11. Last year it got below 36º on Sept. 24, which temperature will kill or damage a lot of annuals and tender herbs. According to Dave's Garden website we have a 80% chance of NOT having anything below 32º by Oct. 4.

If anyone wants to predict the date of the first below 32º I will list the winners in this column/blog after the occurrence. I am predicting Oct. 24. The overall winner (closest to the date) will get a free ticket to the Evanston Garden Walk next June.