The United Kingdom has a predominantly temperate climate, characterised by cool temperatures and consistent rainfall throughout the year. Seasonal temperature variations are generally moderate, rarely dropping below 0 °C (32 °F) or rising above 30 °C (86 °F). Inland upland areas of England, Wales, Northern Ireland, and much of Scotland experience a subpolar oceanic climate, while higher elevations in Scotland see a continental subarctic climate, with mountainous regions approaching tundra conditions.

Prevailing southwesterly winds from the Atlantic Ocean bring mild, wet weather to most of the country, with western regions receiving the majority of rainfall. Eastern areas are largely sheltered from these winds and tend to be drier. The Gulf Stream helps moderate winter temperatures, particularly in the west, while summers are warmest in southeast England and cooler in northern areas. Snowfall can be heavy on high ground during winter and early spring, occasionally settling deeply even in lowland regions.

Sunshine in the UK averages around 1,340 hours annually, roughly 30% of the maximum possible, varying between 1,200 and 1,580 hours depending on location. Since the mid-1990s, annual sunshine hours have generally been above the long-term average.

Climate change is having an increasing impact on the UK, contributing to rising food prices and posing environmental challenges. In 2024, the UK ranked fifth out of 180 countries in the Environmental Performance Index. Legislation has been enacted committing the nation to achieving net-zero greenhouse gas emissions by 2050, reflecting its proactive approach to addressing climate and environmental concerns.