A freeze in the second half of May in Cincinnati is rare. While rare, freezes and frosts and do occur in late May.

The official low temperature this morning at the Cincinnati/Northern Kentucky International Airport was 31°. This sets a new record low temperature for May 16th; the previous record for May 16th was 32°, set in 1997. Low temperatures in the low to mid 30s were widespread this morning:

Inside the I-275 loop, temperatures were slightly warmer due to the urban heat island effect (more building/concrete to retain heat):

Notice Okeana dropped to 28°. Two weather stations just north of Lebanon reported low temperatures of 29° and 28°. Several sites reported a low of 30° or 31°.

How rare is a low temperature of 32° in mid or late May in Cincinnati? Here are the latest spring dates in the Queen City with a low temperature of or below 32°:

Notice that today’s low of 31° is the 3rd latest spring freeze date on record (back to 1871).

Frost can occur at various temperatures, but 36° or below is a good threshold to use for frost. Using 36° as a baseline, here are the latest spring frost dates in Cincinnati back to 1871:

Today’s low of 31° ties as the 9th latest spring frost date in the Queen City. A freeze (which we had this morning) implies widespread frost.

I am cautiously optimistic that this morning will be the last freeze and frost of the season. There are no forecast overnight lows in the 30s through this weekend. Additionally, history suggests we’re safe from a freeze or frost once we get into June!