San Diego sits on the Pacific coast at the southwestern corner of the United States, just north of the Mexican border at approximately 32.72°N, 117.16°W. Cooled by the cold California Current, it has a semi-arid Mediterranean climate (Köppen BSk/Csb) — with famously mild, equable temperatures year-round and very little rain.

Summer, from June to September, is warm and dry rather than hot, with August the warmest month — average highs around 25–26°C — kept remarkably mild by the cold California Current and the reliable sea breeze. Rain is essentially absent, and morning coastal fog and low cloud — the 'May gray' and 'June gloom' — often veil the coast before burning off.

Winter, from December to February, is mild and the wetter season, with January the coolest month — average highs around 19°C and cool nights near 10°C, with frost effectively unknown on the coast. Pacific storms bring most of the year's modest rain, though sunshine remains plentiful between the fronts.

San Diego is very dry, receiving only around 260 mm of rain a year — semi-arid levels — almost all of it between December and March, while the summer is essentially rainless; the cold offshore current suppresses rainfall and feeds the coastal fog. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

San Diego's climate is often called the most equable in the continental United States, its temperature varying by barely 7°C between the coolest and warmest months, thanks to the cold California Current. The exception is the Santa Ana wind, a hot, dry gust off the desert that can bring sudden heat and severe wildfire danger in autumn.

To follow any single measurement in San Diego 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.