The highest average temperature in Houston is July at 85 degrees. The coldest average temperature in Houston is December at 53.5 degrees. The most monthly precipitation in Houston occurs in January with 0 inches.The Houston weather information is based on the average of the previous 3-7 years of data.Loading...he Houston, TX air quality index is 0.8% less than the Texas average and 4.6% greater than the national average. The Houston, TX pollution index is the sum of the most hazardous air pollutants displayed in pounds.