Based on the consecutive observational data per ten minute from 70 surface stations on the National Automatic Weather Observational Net during from 2013 to 2016 in Jiangsu Province, the temporal-spatial distribution patterns of summer heavy fog and its meteorological influence factors are analyzed. The results show that: (1) The heavy fog tends to be formed under the condition that the temperature is less than 29℃, the wind speed is slower than 3 m·s-1 and prevailing in the easterly wind. The low temperature and high humidity during the Meiyu season are probably the causes for the summer heavy fog with a higher frequency (42.4%) in June. (2) The diurnal variation of summer heavy fog is significantly different from the diurnal variations in autumn and winter. The heavy fog mainly appears from 00:00 BT to 06:00 BT and dissipates from 05:00 BT to 08:00 BT, and the duration is mainly within 6 hours. (3) Summer fog is mainly radiation fog. The radiation fog, advection fog and front fog account for 58.1%, 35.5% and 6.4% respectively. (4) The frequency of heavy fog presents a general decrease trend from the northeastern coastal region to the southwestern inland because the cooling rate in the north of the Huaihe River of Jiangsu is higher than that in the southern Jiangsu. (5) The weak rainfall of 6-24 h before the fog formation provides water vapor to the near-surface layer. After that, the weather clears with the stable atmosphere statically, which is beneficial to the appearance of summer heavy fog.