The climate of Islamabad has a humid subtropical climate, with five seasons: Winter (November–February), Spring (March and April), Summer (May and June), Rainy Monsoon (July and August) and Autumn (September and October). The hottest month is June, where average highs routinely exceed 38 °C (100.4 °F). Wettest month is July, with heavy rainfalls and evening thunderstorms with the possibility of cloudburst and flooding. Coolest Month is January. Islamabad’s micro-climate is regulated by three artificial reservoirs: Rawal, Simli, and Khanpur Dam.
The latter is located on the Haro River near the town of Khanpur, about 40 kilometres (25 mi) from Islamabad. Simli Dam is 30 kilometres (19 mi) north of Islamabad. 220 acres (89 ha) of the city consists of Margalla Hills National Park. Loi Bher Forest is situated along the Islamabad Highway, covering an area of 1,087 acres (440 ha). Highest monthly rainfall of 743.3 millimetres (29.26 in) was recorded during July 1995. Winters generally feature dense fog in the mornings and sunny afternoons. In the city, temperatures stay mild, with snowfall over the higher elevations points on nearby hill stations, notably Murree and Nathia Gali.
The temperatures range from 13 °C (55 °F) in January to 38 °C (100 °F) in June. The highest recorded temperature was 46.6 °C (115.9 °F) on 23 June 2005 while the lowest temperature was −6 °C (21.2 °F) on 17 January 1967. The city has recorded snowfall. On 23 July 2001, Islamabad received a record breaking 620 millimetres (24 in) of rainfall in just 10 hours. It was the heaviest rainfall in Islamabad in the past 100 years and the highest rainfall in 24 hours as well.