The climate of Houston is classified as a humid subtropical climate, with tropical influences. August normally ranks as the warmest month at and January the coldest month at . The normal annual precipitation measures . Rainfall is ample throughout the year, though dry spells do occur. Severe weather of Houston mostly takes the form of flooding, which occurs most commonly in the months of May to October, which is the city's monsoon season. Supercell thunderstorms sometimes bring tornadoes to the area, most commonly during spring. Houston sometimes experiences tropical cyclones during the Atlantic hurricane season, which can bring heavy rain and significant damage to the city. The last hurricane to hit was Hurricane Nicholas in 2021. Seasonal observation Temperature-wise the city (and much of Southeast Texas) has four distinct seasons (Summer, Spring, Fall, Winter), but weather wise the city has only two seasons (rainy and dry). The wet season lasts from April/May to September/October, the dry season lasts from November/December to March/April. However during El Nino or La Nina years the wet and dry season can often either last longer than usual or be delayed. Summer June through August in Houston is very hot and humid, often with scattered afternoon showers and thunderstorms. At George Bush Intercontinental Airport, the normal daily high temperature peaks at on 5–12 August, with a normal of 102.4 days per year at or above and 3.5 days per year at or above . The average relative humidity ranges from over 90 percent in the morning to around 60 percent in the afternoon. Summer temperatures in Houston are very similar to average temperatures seen in tropical climates, such as in the Philippines and the lower elevations of Central America. The value of relative humidity results in a heat index higher than the actual temperature. The highest temperature ever recorded at George Bush Intercontinental Airport was on September 4, 2000 and on August 27, 2011. On June 29, 2013, the temperature at George Bush Intercontinental Airport reached , the highest ever recorded in June. Heat stroke can strike people who stay outdoors for long periods of time during the summer, making hydration essential for outdoor work and recreational activity. The 2014 summer season did not yield 100+ degree weather in response to the monsoon-esque rainfall during late June to August, during a period where the Pacific Coast off Central America was heating up, which evolved into the