Frosts in the fall signal the end of the growing season. Strictly speaking, frosts are when we get ice forming.  This can happen and the temperatures are above freezing.  Freezing is when the temperature drop below 32F or 0C.  Freezing temperatures will kill cold sensitive plants like tomato and corn and kill all the leaves on some perennials such as grapes. Hardier plants like apples suffer little damage, but frozen apples should be allowed to thaw before they are harvested.

I have an old MSU publication from 1965, that lists the probability of a frost for some of the older US Weather Service recording weather stations in our region. I have extracted a partial table showing the probability of freezing temperatures for some SW Michigan sites. This table has three threshold temperatures;

• 32, the temperature at which water freezes. This may or may not be a freezing event; we could have only dew but no ice at that temperature.
• 30 will cause damage to all cold sensitive plants. As many early fall freezes are radiation freezes, a temperature of 30 may leave higher elevations unaffected.
• 28 is well below freezing and will kill cold sensitive plants like tomato and corn and kill all the leaves on grapes.

The table below is arranged from North to South. Sites located away from Lake Michigan show the approximate distance to the lake. Sites near Lake Michigan show no distance. In the table 10% means there is a 10% chance of a freeze occurring on or before that date.

For more Michigan climate information including frost dates and other growing season information, check out the Michigan State Climatology Site. Click on the Michigan Map Link and choose the region you are interested in.