The city lies within the humid continental climate zone, and experiences four distinct seasons. Summers are hot and humid, with a July daily average of 84.7 °F (29.3 °C). In a normal summer, temperatures exceed 90 °F (32 °C) on 21 days. Winters are cold, snowy, and windy, with some sunny days, and with a January average of 23.5 °F (−4.7 °C). Temperatures often (for 43 days on average) stay below freezing for an entire day, and lows below 0 °F (−18 °C) occur on eight nights per year. Spring and autumn are mild seasons with low humidity.According to the National Weather Service, Chicago's highest official temperature reading of 107 °F (42 °C) was recorded on June 1, 1934, and July 11, 1936, both at Midway Airport. The lowest temperature of −27 °F (−33 °C) was recorded on January 20, 1985, at O'Hare Airport. The city can experience extreme winter cold waves and summer heat waves that may last for several consecutive days.