Virtually since the end of the last glaciation 12,000 years ago, the weather has managed to get humid here in the Northern Plains at least a few days each summer.
We don’t make the humidity here; it is imported. The source region for our stickiest air in summer is, of course, the Gulf of Mexico, but robust crops of corn and soybeans throughout the Midwest can add a little more sweat to the mix. Evapotranspirative processes within green plants do actually add humidity to the air. Fields of beans and corn are more effective than native prairie grasses. The more robust the beans are, the more humidity they produce.
At our most humid, the summer air can be a few degrees of dew point higher than in Florida. Most of the humidity, to be sure, comes from the Gulf, but the crops between there and here do add a small percentage.