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This page was developed for many reasons, but one of the primary reasons, was to help educate and inform both our clients and general public of the severe weather and tornado climatology of our coverage region, individual states within the region, as well as local climatology data for central Wisconsin. This page also serves as a part of our severe weather "historical Vault", which contains data and statistics dating back to 1950, when reliable severe weather records began. Prior to 1950, any data or statistical piece of information is considered as "preliminary", since it has not been affirmed by the Weather Bureau, which is now the National Weather Service. Please remember that all data and statistics found on this and corresponding pages, are solely for our coverage region, unless otherwise specified. If you wish to view statistical data for the country, please use this link.


Click on tabs to reveal other data.

    COMPOSITE         |          TORNADOES         |          LARGE HAIL         |          DAMAGING WINDS


The severe weather season for our coverage region typically runs from April 1st through September 30th of each year. The months of peak activity are generally from April through July, but peaks in activity can occur at other times during the year as well. On average, our coverage region experiences about 972 tornadoes per year based on data from 1980 to 2010. The states with the highest yearly totals are Iowa and Illinois. By far though, large hail and/or damaging wind events are most common, with dangerous lightening ranking third. While less common then the other mentioned events, flash floods and river flood events rank fourth. It is very noteworthy that the overall death rate from severe weather events across our region remains very low despite the number of storm events. Just from tornadoes alone, the overall total number of related deaths across our coverage region was 206 during the period from 1980 to 2010. This equates to a yearly average of 34 deaths. This is down markedly from the previous total number of deaths. For all forms of severe weather, it appears that large hail reports is trending higher, while severe wind reports is trending downward for the coverage region. Figure 1 illustrates the cumulative severe weather reports from across our coverage region.


The overall trend for major tornadoes across our coverage region appears to be in a steadily declining state. This is largely due to less frequent clashes between warm moist Gulf air streaming north, and cooler drier Canadian air streaming southward. The overall positioning of the primary jet stream either further north or south of our region too, has resulted in less favorable major tornado producing patterns getting into our coverage region. Tornado related fatalities remains about the same, though may have notched up a tad in recent years. Figure 2 shows the number of violent (killer) tornadoes which have been reported in the coverage region from 1950 to 2010, and the respective trend. Violent tornadoes are considered F3 to F5 on the Fujita tornado scale (or EF3 to EF5 on the enhanced Fujita scale).


The overall tornado trends (all tornado intensities), over the past 3 decades across our coverage region have trended downward, while both related injuries and deaths have trended upward. However, the overall death trend from tornadoes has nudged upward only slightly, while injuries are trending upward a bit sharper. One of the primary reasons for this downward trend in tornadoes appears largely due to changing climatology, and positioning of the winds aloft (jet stream) across the conus (contenential U.S.), as well as surface system placement. These factors alone, have resulted in fewer setups across our region which favors tornado and severe thunderstorm development on a broader scale. Continued education and outreach efforts to help the general public obtain an increased knowledge and understanding of tornadoes and severe thunderstorms, their causes, prediction, and the differences between watches and warnings, have led to fewer related deaths overall. To best illustrate this, take a peak at figure 3 below, which shows the state by state breakdown of tornado events.


By contrast, you can see how the numbers stack up for the country in figure 4 below.


Many people have wrote into our office in recent years asking similar questions such as, is there a place where tornadoes occur most? or Why don't our region see as many tornadoes as say, Kansas, Missouri, or even Oklahoma? Those are good questions, and the answers may suprise you. Ever since official tornado and severe weather forecasting begun in earnest back in 1954 with SELS, which means "Severe Local Storm Warning Center", studies were done on those areas of the lower 48 states, where tornadoes were reported. Based on those studies, it was found that the vast majority of tornadoes that were reported and affirmed by the Weather Bureau, struck in a corridor which extended from Texas north to Nebraska, then east to Illinois. This then extended south to Mississippi. Initially, this area was dubbed as "tornado playground" owing to the frequency of such storms. It should be noted here, that the phrase "tornado playground" originated from two Air Force forecasters, E.J. Fawbush and R.C. Miller, who made the very first ever tornado forecasts for Tinker Air Force Base in Oklahoma in March of 1948. Later in 1956, a forecaster at SELS began using aother phrase "tornado alley". That phrase caught on and the media immediately began using it to describe those areas of the central plains which had the greatest number of tornadoes each year. But officially, the phrase "tornado alley" is not used by National Weather Service since research studies have not clearly been able to accurately depict a single area of greatest cumulative tornado totals on a yearly basis. However, in 2000, a group of research scientists, climatologists, and some meteorologists did a study of how the changes taking place in the atmosphere across the contenential U.S. may affect existing and future atmospheric patterns. The study involved the use of many advanced supercomputers which ingested current data, and then modeled trends into the future. The results of that study, though not conclusive, do suggests that tornado alley may have shifted more east and a bit more north. Figure 5 shows the original tornado alley from 1956 through 2004, when the above mentioned study completed. The blue shaded areas on this graphic illustrates how tornado alley has expanded in coverage based on the findings of the study from 2000. Keep in mind that this shows tornado alley across our coverage region only.

Fig. 5

As for the the lower 48 states, the area from the southern plains north across Nebraska and Iowa, then south to Mississippi receives the highest number (frequency), of reported tornadoes each year based on square miles. Florida and southeast states also receive quite a number of tornadoes per year as well. Though the phrase "tornado alley" may never be officially considered a term which describes the highest annual frequency of such events by the National Weather Service, it does provide some interesting ideas of where tornadoes happen most.

Fig. 6

Annual days with thunderstorms across our coverage region varies from north to south, with southern areas receiving more days per year with thunderstorms. One primary reason for this is because those locations are within or close to where battle zones with warm air and cold air often occur. However, such battle zones can and occasionally do happen across our coverage region too. In figure 7 we have listed several city locations within our coverage region, and their computed days per year with thunderstorms. Those numbers shown are for non or sub severe thunderstorm events only.

Thunderstorms Fig. 7

In figure 8 below, is a graphic which outlines the annual thunderstorm days by color contours for each value shown.

Fig. 8

So far, we have presented a basic insight of some aspects of the overall tornado and severe thunderstorm climatology for our coverage region. But the climatology factor goes further then shown on this page. Shown below are links to other pages on this web site where you can learn more information and statistical facts for our coverage region, specific states within our region, and for Wisconsin, which also includes local data from central Wisconsin. Feel free to check them out!

  • All about tornadoes: Learn about these deadly storms here.
  • Wisconsin Tornado Data: Find out the current local and state tornado statistics here.
  • Regional Tornado Data: Current state by state tornado tallies here.
  • Historical Tornado Facts: Learn about some famous tornado outbreaks in our region here.

    Note: Much of the data included on this and corresponding pages was obtained from official data from the NCDC, or "National Climatic Data Center", and "National Weather Service" datasets. Monthly tornado totals and deaths are "preliminary" and considered unofficial. For official information, consult the publication entitled "Storm Data", which is issued by the NCDC.