Houston sits on the low, flat Gulf Coastal Plain of southeastern Texas, about 50 km from the Gulf of Mexico near Galveston Bay, at only around 15 metres elevation and approximately 29.76°N, 95.37°W. It has a humid subtropical climate (Köppen Cfa) strongly influenced by the warm Gulf, with long, hot, intensely humid summers and short, mild winters, and it sits squarely in the path of Gulf hurricanes.

Summer is long, hot and oppressively humid, running from around April to October, with August the hottest month — average highs around 35°C — and the Gulf moisture pushing the heat index well past 40°C, making air conditioning essential. The city has its own irregular summer monsoon of afternoon thunderstorms, and late summer into autumn is the peak of hurricane season, when Gulf storms can bring catastrophic rain, wind and flooding.

Winter, from December to February, is short and mild, with January the coolest month — average highs around 17°C and lows near 6°C. Most days are pleasantly warm, but brief, sharp cold snaps can push in from the north, occasionally bringing frost and, rarely, a little snow. These cold spells are short-lived, and warm, humid Gulf air soon returns.

Houston is very wet, receiving around 1,260–1,300 mm of rain a year on average, with the wettest period toward the end of the warm season; totals can swing wildly, and the flat, low terrain makes the city acutely prone to flooding. The most extreme example was Hurricane Harvey in 2017, which dropped over a metre of rain and caused catastrophic flooding. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Flooding from tropical systems is the defining hazard of Houston's climate: its low, flat, fast-developing terrain beside the warm Gulf leaves it dangerously exposed to the torrential rains of hurricanes and tropical storms, from Tropical Storm Allison in 2001 to the record-shattering Harvey in 2017. Between storms, the relentless combination of heat and Gulf humidity dominates much of the year — Houston was once called the most air-conditioned city in the world.

To follow any single measurement in Houston 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.