Changsha experiences a humid subtropical climate, with annual average temperature being 17.03 °C (62.7 °F), with a mean of 4.6 °C (40.3 °F) in January and 29.0 °C (84.2 °F) in July. Average annual precipitation is 1,331 millimetres (52.4 in), and the frost-free period lasts 275 days. With monthly percent possible sunshine ranging from 19% in March to 57% in August, the city receives 1,545 hours of bright sunshine annually. The four seasons are distinct. The summers are long and very hot, with heavy rainfall, and autumn is comfortable and is the driest season. Winter is chilly and overcast with lighter rainfall more likely than downpours; cold snaps occur with temperatures occasionally dropping below freezing. Spring is especially rainy and humid with the sun shining less than 30% of the time.The minimum temperature ever recorded since 1951 at current Wangchengpo Weather Observing Station was −12.0 °C (10.4 °F), on 9 February 1972. The maximum was 40.6 °C (105.1 °F) on 13 August 1953 and 2 August 2003 (unofficial record of 43.0 °C (109.4 °F) was set on 10 August 1934).