It got chilly last night and early this morning. A number of locations dropped below 40 degrees. In fact, a weather observer at Peavey Falls in Iron Country dropped to 33 while another one north of Ishpeming reported a temperature below the freezing mark at 31. There was even a tinge of frost on the roofs at that location. The NWS reported a low of 32 degrees three times in the past on June 9th??in 1966, 1971 and 1977.
I??ll occasionally have someone ask when is a safe time to plant. In some spots, in the U.P., it??s always a shaky proposition. One of the problems is poor soil and another is chilly nights. Looking back in the records, the NWS has been to freezing as late as June 22nd back in the infamous ??Year without a Summer?? back in 1992. That same year, Iron Mountain reached 31 on June 21st. In the Copper Country, it??s been to freezing as late as June 10th, while in Ironwood the temperature dropped to 29 degrees as late as June 24, 1979.
These late cool nights can make for a short growing season. For instance, in Ironwood it dropped to 32 degrees as early as August 4, 1907. That gives a potential short growing season of just 41 days. The situation is better, but not by much, at Iron Mountain. The earliest freezing temperature in the fall came on August 26, 1945 at 30 degrees. That??s a potential short season of 63 days??way too short for growing tomatoes.
Some of the coldest spots have even shorter growing seasons. For instance at Champion in western Marquette County, the median number of days above 32 degrees is only 67 days. In the 30 years from 1971-2000, the longest growing season (days above 32) was 106 days. The shortest only 4 days!
It will be another cool tonight. If skies clear out completely, there is the potential for some of the traditional cold spots to get down into the 30s again.