Texas' weather varies widely, from arid in the west to humid in the east. The huge expanse of Texas encompasses several regions with distinctly different climates: Northern Plains, Trans-Pecos Region, Texas Hill Country, Piney Woods, and South Texas. Generally speaking, the part of Texas that lies to the east of Interstate 35 is subtropical, while the portion that lies to the west of Interstate 35 is arid desert.
Texas ranks first in tornado occurrence with an average of 139 per year. Tropical cyclones can affect the state, either from the Gulf of Mexico or from an overland trajectory originating in the eastern Pacific Ocean. Those originating from the Gulf of Mexico are more likely to strike the upper Texas coast than elsewhere. Significant floods have occurred across the state throughout history, both from tropical cyclones and from stalled weather fronts.
Characteristics by region
Northern area
The Northern Plains' climate is semi-arid and is prone to drought, annually receiving between of precipitation, and average annual snowfall ranging between , with the greatest snowfall amounts occurring in the Texas panhandle and areas near the border with New Mexico. During the summer, this area of state sees the most clear days. Winter nights commonly see temperatures fall below the freezing mark, or . The wettest months of the year are April and May. Tornadoes, caused by the convergence of westerly and southerly prevailing winds during the late spring, are common, making the region part of Tornado Alley. Poor land management, drought, and high wind speeds can cause large dust storms, minimized in modern times by improved land-management practices, but most troublesome in the 1930s during the Dust Bowl period. The panhandle region, farthest from the Gulf of Mexico, experiences colder winters than the other regions of Texas, where occasional wintertime Arctic blasts can cause temperatures to plunge to well below freezing and bring snowy conditions.
International areas with comparable climate: Southern China; North Argentina; New South Wales, Australia.
Trans Pecos Region
The Trans-Pecos region, also known as Big Bend Country, is in the west-central and western parts of the state, consisting of the Chihuahuan Desert and isolated mountain ranges. During fall, winter, and spring, it experiences the most clear days statewide. It is also the driest receiving an average annual rainfall of only or less. Snowfall is rare at lower elevations, although the highest mountain peaks are prone to heavy snowfalls during winter. The arid climate is the main reason for desertification of the land, but overgrazing is slowly widening the land area of that desert. In the mountain areas one can see coniferous forests in a wetter and more temperate environment. The wettest months in this region occur during the summer. Winds are strengthened as they are forced to push through canyons and valleys. In the flatter areas these winds are harvested into usable electricity.
International areas with comparable climate: Iraq; Iran; Sahel region in Africa
Hill Country
The Texas Hill Country, or central Texas is shaped by its many rivers and hills. The climate is semi-arid west of Brady through Junction to Rocksprings, but it is sub-humid east and south of that area; both areas have hot summers and mild winters with occasional cold spells. Humidity is high during the warm season, though afternoons especially further northwest can see a wind shift and drier air before Gulf air returns after sunset. The vegetation is both broadleaf evergreen and deciduous in the river valleys, and coniferous where there is greater elevation. Dry savannas, open woodlands, and shorter grasses dominate the northwest, while closed woodlands and moist savannas mix with taller grasses in the east and south. In a single year the region can receive up to of precipitation, and flooding is common near rivers and in low-lying areas, while drier years might receive only of precipitation; average annual precipitation ranges from in western sections up to in southeast. The wettest months of the year are April and May.