Freeze warnings are issued from May to October (but can be extended if necessary), when low temperatures are expected to be 29-32 degrees. If there is a potential for temperatures to fall into these thresholds, a freeze watch may be issued a few days ahead of time.

A sudden and sharp drop in temperatures has triggered freeze warnings across 16 states in the U.S., stretching from the Northeast and Midwest to southern and western states, as early-season cold air surges across the country.

Freeze warnings are issued from May to October (but can be extended if necessary), when low temperatures are expected to be 29-32 degrees. If there is a potential for temperatures to fall into these thresholds, a freeze watch may be issued a few days ahead of time.

The warning was for John Day Basin, Foothills of the Southern Blue Mountains of Oregon and North Central Oregon.

"Subfreezing temperatures as low as 24 [degrees Fahrenheit] expected" in some areas of Minnesota and North Dakota, the NWS said.