Why are winter temperatures so low in Austin, Texas, USA?

The climate is similar to that in southern my country

Most of Texas has a temperate climate, and some areas in the south have a subtropical climate. The southern area along Mexico is susceptible to typhoons;

Houston is the fourth largest city in the United States. It is located in Texas and has a subtropical climate. The annual average temperature is 20.7 degrees Celsius and the average annual rainfall is 1. 224mm. There are 188 days of sunshine throughout the year, and there are many hurricanes from July to November every year. The climate is long in summer and short in winter. Summer is hot and humid, starting in May and not getting really cool until October. The highest temperature in summer is generally 32 to 36 degrees, and the temperature exceeds 40 degrees for 7 to 10 days every year, often in early September; the temperature exceeds 33 degrees Celsius for 94 days. The climate is warm in winter, but there are also 7 to 10 days with the lowest temperature at zero degrees or below, usually in January. Although temperatures can drop below freezing at night, they rise again during the day. It rarely snows in winter.

San Antonio

San Antonio, Texas, has a mild climate, with more than 300 sunny days throughout the year, and the average annual temperature is around 20 degrees

Austin, the capital of Texas, has a mild climate and abundant sunshine, with an average of 300 days of sunshine per year. Annual rainfall is about 28 inches, and snow is rare.