Cooler and wetter conditions for the rest of the growing season are pointing to a late harvest, according to state and national agricultural meteorologists, which likely has Iowa farmers questioning whether their crops are going to reach full maturity this fall.

“As you can imagine, I get this question a lot and it’s always very difficult to pinpoint conditions one season out,” said Justin Glisan, Iowa state climatologist. “An anomalously wet fall and winter (both the third wettest in 147 years of state records), on top of 2018 being the second wettest on...