Belfast, the capital of Northern Ireland, sits at the mouth of the River Lagan where it meets Belfast Lough on the northeast coast of the island of Ireland, at approximately 54.60°N, 5.93°W. It has a temperate oceanic climate (Köppen Cfb) — mild, damp, cloudy and changeable — with cool summers, mild winters and rain spread liberally through the year, all moderated by the surrounding Atlantic waters so that extremes of heat and cold are rare.

Summer, from June to August, is cool and often cloudy, with July and August the warmest months — average highs around 18–19°C and cool nights. Hot days are uncommon, and even in high summer showers are frequent, though warm, brighter spells do occur and the long northern days bring plenty of light. It is among the drier and sunnier stretches of the year.

Winter, from December to February, is mild and wet rather than cold, with January and February the coolest — average highs around 8°C and lows near 2–°C. The Atlantic keeps genuinely cold spells, hard frost and lying snow relatively infrequent, so winters are typically grey, damp and breezy, with Atlantic fronts and the occasional gale bringing the most disruptive weather.

Belfast is quite wet, receiving on the order of 900–950 mm of rain a year, falling on a large number of days and spread through every month with an autumn and winter maximum — a reflection of its exposure to the moist Atlantic air that sweeps across Ireland. Rain is more often light and persistent than torrential. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Belfast's weather is characteristically soft and grey — the frequency of light rain and cloud, rather than any severity, is what defines it — and the moist Atlantic air that keeps Ireland famously green also keeps the city damp. Sheltered somewhat within Belfast Lough and by the surrounding hills, it escapes the worst of the Atlantic gales that batter the more exposed north and west coasts, though autumn and winter storms still bring wind and heavy rain.

To follow any single measurement in Belfast 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.