Many Hoosiers circled October 12 as the date of the first heavy frost in their area this year. For many, the first 36 and 32- degree reading came on the same night. For some, the mercury even bottomed near 28 degrees, all in one fell swoop.
The question for ag climatologists is that was the frost right on time, late or early? And while it might seem like a moot point, it could have consequences for future planning and future selection of hybrids and varieties.
Here's the dilemma. Frost-data, like most other weather information, is based on 30-year averages. For years the average frost date in Indiana has been figured on data from a period such as 1940-1970. Average frost dates and predictions of the odds fof a frost coming earlier or later than that are based upon those 30-year patterns.
For many years, the average date in central Indiana, in Indianapolis and surrounding counties, for the first 32 degree frost has been around Oct 5 to Oct 15. This year's Oct. 12 date would fall close to the middle, maybe slightly to the late side. But it also is a harder one to figure because the date of the first 28 degree reading is usually three weeks to a month later, and this time, for some, it came at the same time. That definitely put it earlier than usual, for that severe of a cold outbreak, even if it was short-lived.
The complicating factor is that Jim Newman, long-time ag climatologist, West Lafayette, Ind., says that the average first frost date is definitely moving later in the fall over the last three decades. He predicts that the next time weather averages are updated and based on a previous 30-yar period, frost dates across most of Indiana will move back (later on calendar) about 9 days. So if the average first frost date was Oct 10 before, it will become October 19. While there isn't a clear explanation for the pattern he's convinced that the delay in the onset of the first frost in the fall is very real.
If Newman is right, then perhaps an October 12 frost was early considering the new trend, compared to the average of the last 30 years. Thirty years ago, a late September frost would have been considered early, and a few of those occurred, most notably in the early to mid-70's.
What's all this mean? If the frost date, on average is moving later, late enough that even when it comes early it's Oct 10-12 instead of Sept 25-30, and if the last killing frost of the spring is also earlier, as the same data indicates, then the growing season is longer. That would argue for farmers being able to take fuller advantage of the growing season with crops with longer-maturity windows.
Make your own decision about whether this year's frost was early, on time, or late. Only time will tell for sure! As the song says, 'see what happens in the next 30 years.'