Any frost in sight for Michigan?

It’s the time of year when we can start expecting frost here in Michigan. Here’s a look at the classic normal dates for first freezes and if any cold temperatures are anywhere in sight.

This map from the Midwest Regional Climate Center gives you an idea of the long-term average first 32-degree reading in the fall. That would actually be called the first freeze. Frost can occur when official temperatures drop to 35 degrees at six feet off the ground. The low spots and temperature variations with a temperature at 35 degrees usually yield some frosty patches.

While the map is a little blotchy, it gives you a great idea of where the cold pockets and warm pockets are in Lower Michigan. The map also gives you a great feel for when the first 32-degree temperature normally occurs.

The dark blue area around Clare has a few very cold spots with thermometers and long-term climate readings. That area can have a freeze in mid-September. The light blue area from near Lansing to Cadillac to interior northern Lower Michigan typically gets a first freeze now, in the last two weeks of September. The dark green areas usually freeze in the first 10 days of October.

Then note the warm spots, with a really odd warm spot. The light green areas typically freeze between October 21 and October 31. Notice a warm area from Frankfort to Manistee to Ludington and Pentwater. The warm Lake Michigan water provides a warming effect when the cold northwest winds blow and bring a freeze inland. Of course the Thumb shoreline is also warm because of the proximity to warm Lake Huron waters. The Detroit area has a pronounced urban heat island effect, usually holding off a freeze until near Halloween.

That’s what normally happens. Does weather here in Michigan ever seem normal? Rarely. We also have the current long-term warming trend of a warmer globe and especially warmer oceans.

So is there any frost in the reasonably accurate 10-day forecast? No. Here is a forecast animation of the temperature deviation from normal over the next 10 days. You don’t see any dark blue, which would be temperatures much colder than normal and able to produce a freeze, or even the lesser cold frost.

You see a short one-day period of slightly cooler than normal temperatures. This is cloudiness and showers during the day holding the warmest afternoon temperatures down into the 60s.

When do I think we will have our first frost? In the interior sections of southern Lower Michigan I’d say it probably happens in mid-October. At the warm places of southern Michigan it will probably be the last week of October. Northern Lower Michigan also shouldn’t have frost inland until mid-October.

This means your tomatoes will continue to ripen. If you are a canner, expect all of those tomatoes just turning red on the vine to ripen over the next few weeks.

I can guarantee one thing in weather- winter will come. Frost and freezing temperatures are just two to six weeks away now, which is much later than the historical long-term average.