The United Kingdom has a temperate, maritime climate, despite its northern latitude. The main factor dominating the U.K.'s climate is the Atlantic Gulf Stream, which results in mild winters and cool summers. Cold snaps in winter and heatwaves in summer usually occur when the prevailing Gulf Stream is displaced by continental or Arctic weather systems. The climate of the U.K. is changeable throughout the year. Seasonal changes and regional variations largely determine annual weather patterns.
Average temperatures for spring ranged from 00 degrees Celsius to 10 degrees Celsius, according to U.K. Meteorological Office data collected between 1971 and 2000. Spring temperatures in northern Britain are much cooler than in the south and west of the region. Spring is frequently rainy, accounting for the phrase "April showers." Snow is not unusual in parts of the U.K. during the spring, particularly in highland regions.
Summers in the U.K. are generally cooler and wetter than in mainland Europe. However, heatwaves can strike when continental air systems displace the Gulf Stream. Meteorological Office data shows mean summer temperatures between 6.11 degrees Celsius and 17.8 degrees Celsius. The south and east of the U.K. is warmer than the north and west.
Rain, wind and fog dominate fall in the U.K. However, long spells of warmer weather, commonly known as "Indian Summers" by the British, regularly occur in September and October. Average fall temperatures in the U.K. range from 2.22 degrees Celsius to 12.8 degrees Celsius. Again, the south of the region is warmer than the north.
The Gulf Stream keeps average winter temperatures in the U.K. around -15 degrees C Centigrade higher than other locations at the same latitude. Average winter temperatures range from around -3.89 degrees Celsius to 8.89 degrees Celsius, with the north much colder than the south. Snow is rare in the south of the U.K. It's not unusual for England's capital city, London, to experience completely snow-free winters.