Hurricanes can occur during this period on the Pacific coast of the USA but they are extremely rare, the last one being in 1935. Tornado A funnel-shaped cloud of violently whirling wind, extending down from a cumulonimbus cloud. Tornadoes are also called twisters. Tornadoes develop from thunderstorms. The width of tornado damage paths can vary from a few yards to over a mile and paths can be as much as 50 miles long.
Damage can often be extremely severe.
The funnel of a tornado is visible due to the water drops and dust and debris sucked up. Wind speeds within the funnel have been estimated as being up to 500mph. In the southern USA tornadoes tend to form most frequently in the early spring, while in the northern USA they are most common in summer. For example, in Iowa most tornadoes occur between April and September, with April and May being the most dangerous months. Most tornadoes occur in the American Midwest, between the Appalachian Mountains and the Rockies.