Like everything else when dealing with weather statistics, it varies depending on where you live, but most of this area only average 10-15 days a year with temperatures at or above 90°. Far western North Dakota would be one a big exception. This means that for only about two weeks of the year do we experience what many of us would describe as extreme heat. Some crops do not favor temperatures above 90 degrees for growth. For example, most growing degree calculations for corn will not use a maximum above 86 degrees. Meaning if the low was 70 and the maximum was 90, instead of using an average temperature of 80 degrees that day, the 90 would be replaced with an 86 degree temperature for an average temperature of 78 degrees, or 28 Degree Days instead of 30.