Freezing temperatures and frost will be a possibility on any clear night later this week and into the weekend due to cold air lingering over the region.
It is certainly is the time of year where such a thing is considered normal. However, the average date of the first freezing temperature of autumn has been sliding later and later.
During the first 30 years of record, the period 1881 to 1920, the average first 32-degree temperature date was Sept. 17. By the end of the century, the 1971-2000 average was Sept. 25.
For the present complete three-decade period, 1981-2010, which is what is considered the current "normal," the average has slipped to Sept. 30. But over the last 10 years, the first frost of fall has averaged Oct. 6.
Any given year may bring frost early or late, but the trend is obvious. Some of this trend is due to the increasing heat from an ever-growing Fargo-Moorhead area. But some of it is clearly due to our warming climate.