We’re in that strip of north zone to the south as well.
I was looking up average last frost date the other day, and I put in my zip code to the old farmers almanac site...
our zip code is a rural/unincorporated one with no actual town ... so the site showed data for the weather station in the town to our east ( about 12 miles away by road)
The date was May 6th!
so I put in the the zip code to the town to the west ( also about 12 miles from us by road) ... and the date was April 15th, which is the date I was expecting...
these two towns are only about 14 miles apart as the crow flies, but the May 6th one is on the river in a valley and the other is up higher on historic prairie ground
I thought that was pretty interesting... here’s the link in case anyone wants to check their zip code
https://www.almanac.com/gardening/frostdates