(Riverton, Wyo.) – When will the first fall freeze occur? For Riverton the average date is September 17th, for Lander it’s September 24th. The folks up in Dubois have already seen one day where the low dipped between 33 and 35 degrees, and the Dubois average for the first fall freeze has already passed. It was August 31st.
See the chart below from the National Weather Service Forecast Office in Riverton for the average first fall freeze dates and the dates from the last four years: