UHI isn't as big of a factor as you'd think it is.
For example... RFD has is sitting at 18 days and ARR is sitting at 21 says. 3/4th of RFD is surrounding by open land and corn fields. ARR is in an entirely rural area, fully surrounded by corn fields. MSN is actually situated in a better location for UHI effects that either of them, but, does have the smaller lakes to the SW/S too contend with.