Some farmers along "The Ridge" in West Michigan's apple country let go a sigh of relief this morning that last night's cold weather didn't bring the disastrous frost that it did last year.
Many weren't that all that worried because they could tell from weather signs and local reports that they weren't in for the same sort of series of hard freezes that severely damaged crops last year. But the farmers had reason to be wary: the Fruit Ridge region of West Michigan has the highest concentration of apple growers in the state, and many lost their entire crops last year when April brought record low temperatures after unseasonably high temperatures in March.
You can apply some of their weather wisdom on frost to your own flower and vegetable garden by watching 12-hour forecasts for these weather conditions:
Clear or cloudy night. A cloudy night during the evening and early morning hours helps trap the heat that the ground and plants have absorbed during the day, which prevents frost. A clear night allows the heat from the earth to radiate quickly, promoting frost. Last night was clear, so one for Jack Frost.
Calm or breezy. Frost has a tougher time forming when there is a steady breeze during the night because the wind contiually mixes the air at ground level with layers only a few feet above that may be warmer. Without such a breeze, farmers will resort to manmade wind from 32-foot high, diesel powered towers found on orchards in The Ridge, or even helicopters. Last night had a steady breeze locally, so one for the farmers.
Dew point. The dew point is the temperature at which water vapor in the air will condense on a surface as a liquid (dew) or solid (frost). On a cold clear night without wind, the ground loses heat faster than the air just above it, causing the formation of dew (fine for plants) or frost (undesirable). The rule of thumb is this: the lowest temperature in early morning will approach the dewpoint temperature taken the evening before. Where I live in Standale, the dew point was at 35° F last evening -- still above the freezing point. One for the farmers.
High ground or gully. Gardens in the same general neighborhood can experience different degrees of frost damage, depending on whether they are situated in a low lying area or on a hill. Since cool air collects at the lowest points of topography, gardens in low areas are in greater frost danger. Even for Jack Frost and the farmers last night, depending on where the farms were located.
The National Weather Service, the latest last freeze we've had in Grand Rapids was June 4, 1945, but the next nine freezes were before May 27. So chances are excellent you can get planting this Memorial Day!