Storm Chasing Tornado Climatology Tornadoes can occur at any time of the year and just about anywhere in the world. However, the unique geography of the United States helps to produce some of the most favorable conditions for their development. The months with the greatest number of tornadoes overall are April, May and June, but tornadoes can and do occur during any month of the year.
Tornado seasons vary in different parts of the United States.
In the Southeast, the peak season for tornadoes is February through April. In the northern Plains, tornadoes are most likely to develop from June through August. The reason for this is that low-level heat, moisture, and instability necessary for tornado formation are usually confined to southern regions early in the year, and only reach northern sections with regularity late in the spring. A secondary season of tornado activity has been observed across the South in late autumn as the jet stream, located well to the north in the summer, migrates back southward to its typical wintertime position. In Tornado Alley , very few tornadoes occur in the morning, while in the Southeast, a significant percentage occur during the night and morning hours.