Houston is located in the gulf coastal plains biome, and its vegetation is classified as temperate grassland. Much of the city was built on forested land, marshes, swamp, or prairie—all of which can still be seen in surrounding areas.

Houston has four major bayous passing through the city: Buffalo Bayou, which runs into downtown and the Houston Ship Channel; and three of its tributaries: Brays Bayou, which runs along the Texas Medical Center; White Oak Bayou, which runs through the Heights and near the northwest area; and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel goes past Galveston and into the Gulf of Mexico.

Geology

Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly-cemented sands up to several miles deep. The region's geology developed from stream deposits from the erosion of the Rocky Mountains. These sediments consist of a series of sands and clays deposited on decaying organic matter that, over time, transformed into oil and natural gas. Beneath these tiers is a water-deposited layer of halite, a rock salt. The porous layers were compressed over time and forced upward. As it pushed upward, the salt dragged surrounding sediments into dome shapes, often trapping oil and gas that seeped from the surrounding porous sands. This thick rich soil also provides a good evironment for rice farming in suburban outskirts that the city continues to grow into near Katy. Evidence of past rice farming is even still evident in developed areas as there is an abundance of rich dark loamy top soil.

The Houston region is generally earthquake-free. While the city of Houston contains 86 mapped and historically active surface faults with an aggregate length of 149 miles (240 km), the clay below the surface precludes the buildup of friction that produces ground shaking in earthquakes. These faults generally move at a smooth rate in what is termed "fault creep."

Cityscape

Skyline District of Downtown

When Houston was established in 1837, the city's founders—John Kirby Allen and Augustus Chapman Allen—divided it into political geographic districts called "wards." The ward designation is the progenitor of the current-day Houston City Council districts—there are nine in all.

Locations in Houston are generally classified as either being inside or outside Interstate 610, known as the "610 Loop" or "The Loop". Inside the loop generally encompasses the central business district, and has come to define an urban lifestyle and state of mind. The appellation “inner looper” carries with it the expectation of someone who appreciates cosmopolitan-style city life.

The outlying areas of Houston, the airports and the city's suburbs and enclaves are outside the loop. Another ring road, State Highway Beltway 8 (also known simply as the "Beltway"), encircles the city another 5 miles (8 km) farther out. The third ring road, State Highway 99 (also known as the Grand Parkway), is under construction.

Houston, being the largest city in the United States without zoning laws, has grown in an unusual manner. Rather than a single "downtown" as the center of the city's employment, five additional business districts have grown throughout the inner-city—they are Uptown, Texas Medical Center, Greenway Plaza, Westchase, and Greenspoint. If these business districts were combined, they would form the third-largest downtown in the United States. The city also has the third-largest skyline in the country (after New York City and Chicago), but because it is spread over a few miles, pictures of the city show—for the most part—the main downtown area.

Climate

The "500-year" flood from Tropical Storm Allison

Houston's climate is classified as humid subtropical. The average yearly precipitation level is approximately 48 inches (1,220 mm). Spring supercell thunderstorms sometimes bring tornadoes to the area. Prevailing winds are from the south and southeast during most of the year, bringing heat from the deserts of Mexico and moisture from the Gulf of Mexico.

Winters in Houston are cool and temperate. While the average high in January, the coldest month, is 61 °F (16 °C), Houston sees an average of 18 days per year of 32 °F (0 °C) or less. Snow is almost unheard of, and typically does not accumulate when it is seen. The last snowstorm to hit Houston was on December 24, 2004—the city's first recorded snowfall on Christmas Eve. The coldest temperature ever recorded in Houston was 5 °F (−15 °C) on January 23, 1940.   Source: Weatherbase

During the summer months, the 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 air tends to feel still and the humidity (averaging over 90 percent relative humidity in the morning in the summer and around 60 percent in the afternoon) results in a heat index higher than the actual temperature. To cope with the heat, people use air conditioning in nearly every car and building in the city. Afternoon rains are common, and for most summer days Houston meteorologists predict at least some chance of rain. The hottest temperature ever recorded in Houston was 109 °F (43 °C) on September 4, 2000.