About Huntsville's Climate
From the National Climatic Data Center (NCDC):
Huntsville has a temperate climate. Summers are characterized by warm and humid weather, with rather frequent thunderstorms. Winters are usually rather cool, but vary considerably from one year to the next.
The city of Huntsville is almost surrounded by the foothills of the Appalachian Mountains. The Tennessee River winds its way westward about 7 miles to the south of the city, and the broad, fertile Tennessee River Valley, with flat to gently rolling terrain, extends to the west. The weather station is located at the Huntsville-Madison County Airport, which is 11 miles southwest of the center of Huntsville. Mountain ridges, with elevations from 1200 to 1600 feet above sea level, are located some 14 miles to the northeast, east, and southeast of the airport.
Cold air masses from the continent are predominant over the area during the winter season, but, at times, mild air from the Gulf of Mexico spreads northward to Huntsville or beyond, and may persist for several days in succession. The contrast between air masses frequenting the region in winter provides a potential source of energy from producing extensive periods of low cloudiness and rain, the result being that four months, December through March, account for about 43 percent of the normal annual precipitation. Severely cold weather seldom occurs.
In the transition from winter to spring, appearances of warm, moist air in place of the cold air become more frequent, and the greatest variety of weather usually occurs during this season. Spring season thunderstorms in the vicinity of the boundary between warm and cold air masses are more likely to be accompanied by locally severe weather conditions than thunderstorms in other seasons.
Day to day changes in the summer season are rather small, other than the occurrence of thunderstorms that provide relief from the heat on about one-third of the days. Temperatures frequently rise to 90 degrees or higher, but reach 100 degrees only on rare occasions.
During the Fall, the weather is usually dry and pleasant. The air masses are cooler in the lower levels and the thunderstorm activity of summer decreases sharply. The dry air is very favorable for the harvesting of cotton and hay crops, important items in the economy of the area. A major departure from the relatively dry weather of fall is an occasional rainy spell of one or more days associated with a decaying hurricane drifting northward from the Gulf of Mexico.
Precipitation amounts for the drier months of the fall are appreciably less than for the relatively wet season in winter. However, with the exception of an infrequent long dry spell, precipitation distribution is such as to provide adequate moisture for plant growth throughout the year. Precipitation is mostly in the form of rain, bt snow can be expected to some extent each winter, and seasonal totals have ranged from less than 1 inch to over 20 inches.
The growing season is 214 days. The climate is suitable for truck farming, as well as for staple crops and livestock. The average date for the last freeze in the spring is late March and the average date of the first freeze is late October.