A daily low temperature of 70 degrees or warmer is uncommon in Fargo Moorhead. We average only three per year and even that number is skewed somewhat by a handful of years with higher totals. Since 1881 there have been 33 years without a single day with a low at or above 70 degrees, including the recent summers of 2008 and 2009.
There are two principal reasons why this area experiences so few 70 degree daily lows. One is the fact that truly humid days (dew points above 70 degrees) are infrequent. Higher moisture content in the air is a key ingredient in keeping the temperature warmer overnight.
The second reason is we do in fact have more 70 degree mornings than the statistics indicate, but daily high and low temperatures are from midnight to midnight and frequently in this area our 70 degree mornings occur ahead of a cold front that often will lead to the temperature falling below 70 degrees before the day is done.