1 Record Coldest year in Kentucky - 1917 / Avg temperature 52.55 degrees. 2  Kentucky average Summer temperature (June, July, August) 74.5 F degrees, 15th warmest U.S. summer state.inters are rarely harsh. In January, average daily high temperatures increase from 38 F in the north to 44 F in the south. Cloudy skies are more frequent in winter, as most areas receive near 40 percent of available sunshine. Polar air masses occasionally affect Kentucky for short periods.