LEXINGTON — It may seem hard to believe, but the National Weather Service – Hastings says south central Nebraska is within two to four weeks of the average date for the first fall frost or freeze.
NWS Hastings will issue Freeze Warnings or Frost Advisories for their coverage area this fall until those counties experience at least one hard freeze, usually 28 degrees or colder.
After this point, additional warnings are considered unnecessary because the growing season has effectively come to an end.
It is noted, the first fall frost and freeze date can, “vary tremendously,” from one year to the next and within the past 30 years, first freezes have ranged from mid-September to early November.
Last year, most of the coverage area had its first true fall freeze and/ or hard freeze sometime between Oct. 16-26.
Looking through this week, there is minimal concern for frost and especially freezing temperatures within the coverage area through at least Sept. 27.
However, early Wednesday morning will likely be the chilliest night of the season so far, with most of the coverage area dropping into the low to mid-40s. However, it’s possible western Dawson, Valley and Greely counties could trend colder toward lows in the upper 30s, but this still appears to be just warm enough to keep frost from becoming a threat.
The NWS Hastings offers some definitions to understand future warnings or advisories.
Frost: Frost occurs when there is a solid deposition of water vapor from the air. Frost will form when solid surfaces are cooled below the dew point. An air temperature range of 33 degrees- 36 degrees, along with very light winds, is usually needed to initiate frost formation. At least minor damage is possible to plants. Keep in mind that a frost is not guaranteed if humidity isn't high enough and/or winds are roughly 8 miles per hour.
The range of average dates for the first fall frost across most of south central Nebraska and north central Kansas is around Sept. 24 - Oct. 8.
Freeze: Freeze occurs when the temperature drops to 32 degrees or lower. A freeze will result in significant damage to many unprotected plants, especially if the temperature remains at or below freezing for several hours.
The range of average dates for the first fall freeze across most of south central Nebraska and north central Kansas is around Oct. 1 - Oct. 16.
Hard Freeze: Hard freeze occurs when the temperature reaches 28 degrees or lower for at least a few hours. It usually means that many types of plants and most seasonal vegetation will be destroyed.
The range of average dates for the first hard freeze of the fall across most of south central Nebraska and north central Kansas is between Oct. 9 - Oct. 26.
Based on a 30 year average from 1991-2020, the earliest date for 32 degrees or lower in the Gothenburg area was Sept. 19, 2006. The latest date was Oct. 27, 2013. The average date falls around Oct. 16 each year.
In a bit of history, NWS Hastings looked back on the unusually early frost and freeze of September 1974.
One of the earliest frost and freezes on record in parts of the south central Nebraska occurred the first week of September 1974. Many locations dropped below the freezing mark as early as Sept. 3. That morning cooperative observers in Beaver City and Revenna reported morning lows as cold as 29 degrees.
A look at the surface weather map recorded at the time shows the reason, an unseasonably cold air mass roared into the region behind a strong cold front. Eventually, surface high pressure set up over the region, creating the ideal situation for a record early freeze.
An observation form from Gothenburg noted, “Clear. Froze. Ice. Crop Damage,” on the right side of the form for Sept. 3.
Another interesting fact is that both Gothenburg and Greely recorded freezing temperatures just 10 days later on Sept. 13. Highly unusual for the time and season.