St. Cloud’s First Frost of the Season is Already a Week Late
Unseasonably warm temperatures were the theme this year for summer, and that seems to be carrying over into fall. St. Cloud's first frost happens on average between September 21st and September 30th, and we have yet to see it appear as we are now in October.
Frost develops when the temperature is cold enough for water molecules in the air to freeze. The process is called Deposition (it’s the opposite of evaporation). Ice crystals appear without liquid water ever forming. This happens most frequently on surfaces that are wet and get cold much faster than the air around it like grassy fields, roof tops, or your favorite frost sensitive plants.
Frost mainly forms on nights that are clear and cold with calm wind. Looking at the forecast for this week we will have plenty of clear and calm, but we are missing the cold as overnight lows stay in the 50s.
The Old Farmer's Almanac predicted our first frost this year to be on September 22nd, sharing a disclaimer:
Note that frost dates are only an estimate based on historical climate data and are not set in stone. The probability of a frost occurring after the spring frost date or before the fall frost date is 30%, which means that there is still a chance of frost occurring before or after the given dates.
It was one of the warmest summers on record in recent history, so it only makes sense that early fall would be experiencing a similar weather pattern. Don't worry, this is Minnesota. You'll be digging your ice scraper out soon enough!