CINCINNATI — Here in Cincinnati, as of early April, we've already enjoyed more than a dozen afternoons in the 70s — and four days in the 80s! These early warm days often tempt gardeners to get outside and start planting, but that can be a mistake.
Parts of the Tri-State will likely drop to or below freezing the next couple of mornings, April 7 and 8. That's not unusual in April. If you have any plants that are sensitive to the cold, you'll need to protect them before heading to bed the next couple of nights.
If you don't want to cover up those more sensitive plants or drag their pots back inside, it's safest to hold off until Mother's Day to put them outside. Your safest bet is to hold off until Memorial Day in late May, and here is why.
In Cincinnati, our average last freeze doesn't happen until April 22, although in 1925, we had to wait until May 25 for the season's last freeze. The average is from the 30-year period of 1991 to 2020.
On average, the last frost doesn't happen until about a week later, on April 30. The latest frost on record, dating back to the 1870s, was on May 29, 1965.
To get these dates, I used a temperature of 36 degrees and lower. That air temperature is taken 2 meters above the surface. Even though that seems like a small distance, the temperature at the surface, where your plants often live, can be around 32 at that point, allowing for frost. Frost formation also requires light wind and enough moisture ... so those dates are estimates.
Since Cincinnati runs a touch warmer than most parts of the Tri-State, here are some average last frost dates for a few other spots in the Tri-State.
- Wilmington, OH: May 2
- Brookville, IN: May 1
- Maysville, KY: May 3
While many of us may not be patient enough to plant until late May, just be ready for a little extra work on these last handful of cold nights and mornings.
