As the climate of North Dakota and Minnesota has warmed over the past several decades, average afternoon temperatures have increased slightly while average nighttime lows have increased a lot more. Interestingly, scorcher afternoons have actually become less frequent. Temperatures in the upper 90s and 100s, always a rarity in our climate, have become even rarer. In fact, the average nighttime temperatures account for about three-fourths of the measured warming in summer.
Much of this counterintuitive warming pattern is related to increased average summer rainfall and humidity, all of which has led to wetter topsoil, which makes those really hot afternoons harder to come by. If the ongoing drought across the Northern Plains continues, very dry topsoil conditions could potentially cause an increase in the frequency of those very hot afternoons in the upper 90s and 100s this summer.