Istanbul has a persistently high humidity, which can exacerbate the moderate summer heat.[75] The humidity is especially salient during the morning hours, when humidity generally reaches eighty percent and fog is very common. The city receives fog an average of 228 days each year, with the highest concentration of foggy days being in the winter months, although it usually dissipates by noontime. Thunderstorms are uncommon, occurring just 23 days each year, but they occur most frequently in the summer and early autumn months.[76] Istanbul has an annual average of 124 days with significant precipitation, which together generate around 844 mm (33 in) of rain. The highest recorded temperature was 40.5 °C (105 °F) on 12 July 2000, and the lowest recorded temperature was −16.1 °C (3 °F) on 9 February 1927.[78] The highest recorded rainfall in 24 hours was 227 millimetres (8.9 in) on 16 October 1985.[78] The highest recorded snow cover was 80 centimetres (31 in) (and more than 60 centimetres (24 in) at the coast) in March 1987.[78][79]