The southern part of Quito has a subtropical highland climate , while the northern part has a warm-summer mediterranean climate (Köppen climate classification Csb). Because of its altitude and location on the equator, Quito has a fairly constant cool climate. The average afternoon maximum temperature is 21.4 °C (70.5 °F), and the average night-time minimum temperature is 9.8 °C (49.6 °F). The annual average temperature is 15.6 °C (60.1 °F). The city has only two seasons: dry and wet. The dry season, June through September (4 months), is referred to as summer; the wet season, October through May (8 months), is referred to as winter. Annual precipitation, depending on location, is about 1,000 mm (39 in).
Due to its altitude, Quito receives some of the greatest solar radiation in the world, sometimes reaching a UV Index of 24 by solar noon.
The fact that Quito lies almost on the equator means that high pressure systems are extremely rare. Pressure is stable, so very low pressure systems are also rare. From 1 July 1 2010 to 30 June 2011 the lowest pressure recorded was 998.2 hPa (29.48 inHg), and the highest was 1,015.2 hPa (29.98 inHg). Despite the absence of high pressure, Quito can still experience settled weather. Generally, the highest pressure is around midnight and the lowest in the mid-afternoon.