1b_Climate
Fort Knox has a humid subtropical climate (Köppen Cfa) with four distinct seasons and is located in USDA hardiness zones 6b and 7a. Spring-like conditions typically begin in mid-to-late March, summer from mid-to-late-May to late September, with fall in the October–November period. Seasonal extremes in both temperature and precipitation are not uncommon during early spring and late fall; severe weather is not uncommon, with occasional tornado outbreaks in the region. Winter typically brings a mix of rain, sleet, and snow, with occasional heavy snowfall and icing. Fort Knox averages 5.8 days with low temperatures dipping to 10 °F (−12 °C), while readings of 0 °F (−18 °C) or below occur on average every several years, the last occurrence being January 7, 2014; the average window for freezing temperatures is October 31 thru April 6, allowing a growing season of 207 days. Summer is typically hazy, hot, and humid with long periods of 90–100 °F (32–38 °C) temperatures and drought conditions at times. Louisville averages 35 days a year with high temperatures at or above 90 °F (32 °C), and the average window for such temperatures on average fall on June 7 and September 10, respectively. The mean annual temperature is 58.2 °F (14.6 °C), with an average seasonal snowfall of 12.5 in (32 cm) and an average annual rainfall of 44.9 inches (1,140 mm). The first and last measurable (≥0.1 in or 0.25 cm) snowfalls of the season on average fall on December 8 and March 12, respectively. The greatest amount of precipitation in 24 hours was 10.48 inches (266.2 mm) on March 1, 1997 and the heaviest 24-hour snowfall total was 15.5 in (39.4 cm), occurring only two days before the all-time record low.