Guthrie is pleasant in spring (April–May) and autumn (September–October) when the heat is manageable and the Victorian brick downtown is at its best in warm afternoon light. The Oklahoma International Bluegrass Festival runs each October, drawing around 15,000 visitors and filling the downtown with live music across multiple outdoor stages — this is the best single reason to time a visit.
Summer (June–August) is hot and humid by Oklahoma standards; the heat can be oppressive midday but the evenings are liveable. Winter visits are generally fine, and the A Territorial Christmas Carol at the Pollard Theatre makes December a reasonable time to visit if you are within range of Oklahoma City.