I assume there were a lot more fields back then with the abundant tree cutting. I wonder how much that helped the region heat up and radiate at night. It tended to be more arid times back then too as the poor farming practices were beginning in the plains and we had fewer GHGs. So those airmasses coming from our west had to be extremely hot and dry...sonoran for like 2 weeks. Being deep in river valleys probably helped Keene and Franklin decouple while Nashua stayed a bit mixed. Of course there’s a “yore” factor where you sometimes have to ask if the data passes the smell check. Many had differing obs times and differences in instrumentation, siting, and observing methods. Maybe Chris has access to info describing what each site used during the history of the station’s existence. But there’s enough consistency in the numbers between multiple sites in multiple states to know these days and days of 100s were legit.