Weather and Climate
The Climate of Houston is classified as humid subtropical. Houston's warmest month (on average) is July at 84.5 °F (29.2 °C), and the coldest month being January at 54.3 °F (12.4 °C). The average yearly precipitation level is 54.0 inches (1,370 mm). Houston has occasional severe weather, mostly in the form of flooding. Spring supercell thunderstorms sometimes bring tornadoes to the area. Houston may sometime experience tropical cyclones during the hurricane season, which can bring significant damage to the city. The last to hit was Hurricane Ike in 2008.
June through August in Houston is very hot and humid, often with regular afternoon thunderstorms. The average daily high temperature peaks at 94 °F (34 °C) at the end of July, with an average of 99 days per year above 90 °F (32 °C). The average relative humidity ranges from over 90 percent in the morning to around 60 percent in the afternoon. The temperatures in the summer in Houston are very similar to average temperatures seen in tropical climates, such as in the Philippines and Central America. The values of relative humidity results in a heat index higher than the actual temperature. The hottest temperature ever recorded in Houston was 108 °F (42 °C) on September 4, 2000. Heat stroke can strike people who stay out of doors for long periods of time during the summer so hydration is essential for outdoor work and recreational activity. Houston's heat and humidity made air-conditioning an essential element in Houston's early survival, and it continues to be important in day-to-day life. Most workers are relatively unaffected by the heat since they spend the hottest part of the day indoors in air conditioning. Air conditioning is considered the stimulus for the growth of Houston in 1950 when it became the most air-conditioned city in the world.
Autumn in Houston is warm, with temperatures averaging in the upper 60s to lower 80s °F (20-28 °C) during the day and in the 50s to lower 60s °F (10-17 °C) at night. Cool fronts that move through the region during the fall can bring rain. Hurricanes can move into the area from the Gulf of Mexico bringing heavy rains and high winds. However, most years see little or no significant hurricane activity. Flooding is most frequent in October and November. Since 1851, the latest a hurricane has impacted Texas was Hurricane Juan (1985), on October 28 of that year.
Winters in Houston are very mild and temperate. While the average high in January, the coldest month, is 63.3 °F (17.4 °C) and the low 45.2 °F (7.3 °C), Houston sees an average of 18 days per year of freezing temperatures. Cold fronts during the winter drop nighttime lows into the 30's, averaging out at 36° F (2.2° C) but usually above freezing. There usually is a period of about three weeks with what would be considered "winter" weather—temperatures in the low 30's to mid-40's. 'Hard freezes' are uncommon. Snowfall, ice and sleet are almost unheard of. Houston receives snowfall on average about once every 3.5 years. The coldest temperature ever recorded in Houston was 5 °F (−15 °C) on January 23, 1930.
In December, southward-moving cold fronts can bring cold rain, low wind chills, freezing rain, and rarely frozen precipitation. Early January is the coldest time of the year, with temperatures moderating by February.
Snow is extremely unusual in Houston. Light snow has fallen approximately 35 times since 1895, more recently on December 4, 2009 and February 23, 2010. Freezing rain, also known as ice storms, are slightly less rare. The most recent ice storms occurred in 1997 and 2007. These storms can be very disruptive since road crews are not equipped to handle such rare events (and motorists are entirely unfamiliar with ice). When ice occurs, road and schools are usually closed.
Spring comes with a gradual warm up from winter, lasting from March 20 through May. Temperatures are generally not hot yet, averaging from 75–82 °F (23.9–27.8 °C) in the day and 56–64 °F (13.3–17.8 °C) at night. Spring thunderstorms are not uncommon, often with spectacular lightning shows. This rainfall prompts Houston's 10-month long "growing season" to begin. April sees the return of many types of insects, including butterflies and mosquitoes, to return to Houston's warm climate.
Rainfall is the most common form of precipitation in Houston. The wettest month is June, with 6.84 inches (174 mm) of rain. The city receives 47.9 inches (1,220 mm) of rain in an average year. The most precipitation to fall in one year was 72.86 inches (1,850.6 mm) which occurred in 1900. Houston has received less than 20 inches (510 mm) of rain only once: 17.66 inches in 1917. Flash flood warnings are common all year, and due to the flat landscape, heavy rains can be a threat to the city.
Sleet, snow and ice are unusual, and sometimes never occur at all during the winter. Hail can accumulate, yet only in small quantities. Frozen precipitation does not survive the warmer temperatures.
(This text above is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Climate of Houston".)
