Houston has a humid subtropical climate, with prevailing winds bringing in the heat from the deserts of Mexico and moisture from the Gulf of Mexico during most of the year. Summers are swelteringly hot and humid, making air conditioning a necessity rather than a luxury. In summer (June to August) temperatures average between 73°F (23°C) and 94°F (35°C), and in winter (December to February) temperatures average between 43°F (6°C) and 66°F (19°C). Summers are characterised by afternoon thunderstorms, which bring rain most days, and sometimes tornadoes. Winters, by contrast, are cool and temperate, with no snow but some rain.