USHCN raw daily data shows that June-September 1954 was the hottest four month period in Oklahoma history
Hottest 4 month periods - average max temeprature Rank Month Year Temperature 1 9 1954 97.7539 2 9 1956 96.793 3 9 1936 96.6953 4 9 1980 96.3008 5 9 1934 95.8691 6 9 2011 95.8516 7 8 1934 95.834 8 8 1936 95.5508 9 9 1998 95.4219 10 9 1952 95.2578