Weather and Climate

Weather vs climate

Weather describes the day-to-day conditions of the atmosphere in a particular place, including temperature, precipitation, wind speed, cloud cover and humidity. Climate, on the other hand, is the average weather conditions of an area measured over a long period, typically 30 years or more. You might say “the weather today is rainy” but “the climate in the UK is temperate maritime.” Understanding this distinction is essential because it underpins the study of both short-term weather events and long-term environmental change.

Factors affecting climate

Latitude

Places closer to the equator receive more direct sunlight throughout the year because the Sun's rays hit the surface at a higher angle. This means the energy is concentrated over a smaller area, producing higher temperatures. As you move towards the poles, the Sun's rays strike at a lower angle and spread over a larger area, so temperatures are lower. This is the single biggest factor determining a region's climate.

Altitude

Temperature drops by approximately 1 degree C for every 100 metres of altitude gained. This is called the environmental lapse rate. Mountain areas are therefore colder than lowland areas at the same latitude. Higher altitude also brings increased rainfall because air is forced to rise over mountains, cooling and condensing to form clouds in a process called relief rainfall.

Ocean currents

Ocean currents transfer heat energy around the globe. The North Atlantic Drift, a warm ocean current, carries heat from the Gulf of Mexico towards north-west Europe, keeping the UK significantly warmer than other places at the same latitude, such as Labrador in Canada. Cold currents, like the Benguela Current off south-west Africa, have a cooling effect on nearby coastlines.

Distance from the sea

Water heats up and cools down more slowly than land. Coastal areas therefore experience milder winters and cooler summers than places inland at the same latitude. This moderating effect is called continentality. London, further from the Atlantic, has slightly hotter summers and colder winters than Cornwall.

UK weather patterns

The UK sits in the path of the polar front jet stream, where warm tropical air meets cold polar air. This makes UK weather highly changeable. Depressions (low-pressure systems) bring cloud, rain and wind, while anticyclones (high-pressure systems) bring settled, dry conditions, hot in summer and cold in winter. Prevailing winds blow from the south-west, carrying moisture from the Atlantic, which is why western parts of Britain tend to be wetter than the east.

Microclimates

A microclimate is a small area where the climate differs from the surrounding region. Urban areas tend to be warmer than rural surroundings due to the urban heat island effect: buildings and tarmac absorb heat during the day and release it at night, while vehicles and industry generate additional warmth. South-facing slopes in the northern hemisphere receive more sunlight and are warmer than north-facing slopes. Sheltered valleys can trap cold air at night, creating frost hollows.

Climate change

The enhanced greenhouse effect is the main cause of current climate change. Human activities, primarily burning fossil fuels, deforestation and agriculture, increase the concentration of greenhouse gases such as carbon dioxide and methane in the atmosphere. These gases trap outgoing infrared radiation, warming the planet. Effects include rising sea levels from thermal expansion and ice-sheet melting, more frequent extreme weather events, shifting rainfall patterns, loss of biodiversity and threats to food and water security. Internationally, agreements like the Paris Agreement aim to limit warming to 1.5 degrees C above pre-industrial levels.