London sits in the southeast of England on the River Thames, in the sheltered London Basin between the Chiltern Hills and the North Downs, at approximately 51.51°N, 0.13°W. It has a temperate oceanic climate (Köppen Cfb) — cool, cloudy and changeable, shaped by a procession of Atlantic weather fronts — but its southern, sheltered position makes it the mildest, warmest and driest of the UK's big cities, and its reputation for rain owes more to the frequency of showers than to the amount.

Summer, from June to August, is mild to pleasantly warm and the sunniest, driest time of year, with July and August the warmest months — average highs around 23–24°C, the warmest in the UK. Settled spells bring genuinely hot days, and heatwaves have become more frequent and intense: the city reached an unprecedented 40.2°C in July 2022, the highest ever recorded in Britain. Even so, Atlantic fronts can still bring cool, showery interludes at any point in the summer.

Winter, from December to February, is cool and damp rather than harsh, much milder than the latitude suggests thanks to the Atlantic, with January the coldest month — average highs around 8°C and lows near 2–3°C. Mild, breezy Atlantic spells alternate with colder, still, foggy high-pressure periods and occasional outbreaks of cold continental air. Snow falls on only around 16 days a year and rarely settles for long, while frost is more common.

London is one of the driest parts of the UK, receiving only around 600–690 mm of rain a year — less than Rome, New York or Sydney — spread fairly evenly through the year with a modest autumn peak around November and a drier spring. The rain is typically light and intermittent, drizzle or brief showers rather than heavy downpours, which is why the city can feel wetter than the totals suggest. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

London's weather is defined above all by its changeability and its cloud — sitting under the path of the polar jet stream, it can serve up several kinds of weather in a single day — and it receives comparatively little sunshine, under 1,700 hours a year. A gentle urban heat island keeps the city centre a degree or two warmer than the surrounding countryside, most noticeably on clear winter nights.

To follow any single measurement in London more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.