Huntsville has a humid subtropical climate . It experiences hot, humid summers and generally mild winters, with average high temperatures ranging from near 90 °F (32.2 °C) in the summer to 49 °F (9.4 °C) during winter.
Huntsville is near the center of a large area of the U.S. mid-South that has maximum precipitation in the winter and spring, not summer. Average yearly precipitation is more than 54 inches. On average, the wettest single month is December, but Huntsville has a prolonged wetter season from November to May, with (on average) nearly or over 5 or more inches of precipitation most of those months. On average, August to October represent slightly drier months (see climate chart, showing less than 3.8 inches of precipitation these months). Droughts can occur, primarily August through October, but usually there is enough rainfall to keep soils moist and vegetation lush. Much of Huntsville’s precipitation is delivered by thunderstorms. Thunderstorms are most frequent during the spring, and the most severe storms occur during the spring and late fall. These storms can deliver large hail, damaging straight-line winds, and tornadoes. Huntsville lies in a region colloquially known as Dixie Alley, an area more prone to violent, long-track tornadoes than most other parts of the US.
On April 27, 2011, the largest tornado outbreak on record, the 2011 Super Outbreak, affected northern Alabama. During this event, an EF5 tornado that tracked near the Browns Ferry Nuclear Power Plant destroyed many transmission towers and caused a multi-day power outage for the majority of North Alabama. That same tornado also resulted in considerable damage to the Anderson Hills subdivision and in Harvest, Alabama. In total, nine people were killed in Madison County, and many others injured. Other significant tornado events include the Super Outbreak in April 1974, the November 1989 Tornado Outbreak that killed 21 and injured almost 500, and the Anderson Hills Tornado that killed one and caused extensive damage in 1995. On January 21, 2010, Huntsville experienced a rare mid-winter tornado. It registered EF2 on the Enhanced Fujita scale and resulted in moderate damage. Because it was not rain-wrapped and was easily photographed, it received extensive media coverage.
Since Huntsville is nearly 300 miles (480 km) inland, hurricanes rarely arrive with their full force; however, many weakened tropical storms cross the area after a U.S. Gulf Coast landfall. While most winters have some measurable snow, heavy snow is rare in Huntsville. However, there have been some unusually heavy snowstorms, like the New Year’s Eve 1963 snowstorm, when 17 in (43 cm) fell within 24 hours. Likewise, the Blizzard of 1993 and the Groundhog Day snowstorm in February 1996 were substantial winter events for Huntsville. On Christmas Day 2010, Huntsville recorded over 4 inches (10 cm) of snow, and on January 9–10, 2011 it received 8.9 inches (23 cm) at the airport and up to 10 inches (25 cm) in the suburbs.