Tornado Climatology Tornado Maps

Peak tornado season is often April or May, but that’s not always the case

Peak tornado season is here. While it is true that tornadoes can happen across the calendar, the spring and early summer is highly favored over other time.

Out of the 71 years in the modern record (since 1950), the peak month for tornadoes has been April a surprisingly-small seven times, May 35 times, and June 25 times.

However, when one looks at strong tornadoes, or those which cause the most havoc and are rated F/EF2+, some different patterns show up. Here we see April the peak month in 25 of the 71 years, May in 23, then March and June with eight each.

You can examine the data in the table below.

YearF/EF0+ high moF/EF0+ highF/EF2+ high moF/EF2+ high
1950May61May21
1951Jun76Jun30
1952Mar43Mar34
1953Jun110May50
1954Apr113Apr50
1955Jun153Apr49
1956Jul92Apr49
1957May228Apr93
1958Jun128Jun42
1959May226May81
1960May201May77
1961May137Mar66
1962May200May73
1963Jun90Apr51
1964Apr157Apr63
1965May273May98
1966Jun126Jun32
1967Jun210Apr68
1968May142Apr49
1969May145Jun54
1970Jun134Apr63
1971Jun199May63
1972May140Apr44
1973May250May95
1974Apr267Apr157
1975Jun196May51
1976Mar180Mar85
1977May228May49
1978May213Apr38
1979Jun150Apr43
1980Jun217Apr50
1981Jun223May57
1982May329May65
1983May249May77
1984Jun242Jun44
1985May182May39
1986May173Mar29
1987Jul163Jul19
1988May132Nov37
1989Jun252May40
1990Jun329Jun62
1991May335Apr53
1992Jun399Jun61
1993Jun313Jun32
1994Jun234Apr25
1995May394May66
1996May235Apr37
1997May225Mar47
1998Jun376Apr38
1999May310Jan46
2000May241Apr23
2001Jun249Nov28
2002May204Nov30
2003May542May80
2004May509May39
2005Jun317Nov35
2006Apr244Mar33
2007May252Mar32
2008May460May77
2009Jun270Apr30
2010Jun321May44
2011Apr757Apr166
2012Apr204Mar38
2013May267Nov34
2014Jun286Apr35
2015May381May27
2016May217May31
2017May291Apr26
2018May170Apr15
2019May511May56
2020Apr251Apr54

Perhaps most interesting is that a number of years — five, to be exact — have a November peak for strong tornadoes.

2013 is an extreme instance of a November tornado outbreak, with all but a handful of its 34 strong tornadoes happening in one event. Other years like 2005 had both very low numbers in spring and summer plus a number of events in November. All of these Novembers did have at least one significant outbreak.

In the “Doppler era,” which I think of as 1995 onward, November is the peak month for strong tornadoes as frequently as March, with four instances each.

As with a lot of tornado stats, any longer-term trends seem mushy. If anything, it would seem there are perhaps a few stories to highlight:

  • May is increasingly the peak of overall tornado season. Not totally surprising. Chasers and dual pol doppler see a lot of low-end stuff we used to miss. More of the country is in play. The jet stream has not yet retreated.
  • June strong tornado peak is a thing of the past? In the last two decades, there have been no June peak years for strong tornadoes. This compares to an average of two per decade prior.
  • Novembers to remember more common? This could be an artifact of increased sensitivity to catching more tornado events. Or it could be in concert with the fact that spring activity has been underwhelming in a number of years.

Below is a map showing which month is peak by state during the Doppler era (through 2019, when SPC data is available).

Since I’m using all tornadoes — including the weakest and loneliest — in the first map, I started with the Doppler era to isolate the period with the least overall number inflation (thanks to better observation) compared to prior years.

The map nicely highlights when various states historically see their greatest tornado risk.

In April’s case it is the South into the Southeast most often under the gun. By May, the zone of activity tends to favor the southern and central Plains into the flatlands of Illinois and Indiana, then off to the Ohio Valley region.

From there, the northern tier and high Plains as well as the mid-Atlantic tend to see the most tornadoes in June, with the northeast usually favoring July.

Although weighted by a few years in the case of Virginia, it’s worth pointing out that a few states have a September peak for tornadoes. This is largely associated with landfalling tropical cyclones, particularly in Florida.

When it comes to strong tornadoes, or those causing the majority of deaths and damages, the map looks relatively similar.

In most of the big tornado states — places like Alabama, Mississippi, Texas, Oklahoma, Kansas — the peak for strong tornadoes is unsurprisingly about the same for the peak of tornadoes overall. There is also a peppering of March in the Southeast and a few changes elsewhere.

Finally, let’s look at how many tornadoes the typical peak month witnesses.

April 2011 delivered an astounding 757 tornadoes, bolstered by the Super Outbreak focused on the 27th. Behind that, the top five months are all May. As recently as May 2019, the United States saw an incredible 511 tornadoes as outbreak after outbreak occurred mid- and late month.

The current 25-year running average is about 335 tornadoes in the busiest month of a year and it has been relatively steady for about a decade. Keep in mind there is inflation over time due to increasing spotter activity and detection technology.

The “strong” tornado category does not see that inflation as much. The current average for strong tornadoes in a peak month is in the mid-40s, near where it has hovered since the advent of Doppler.

1974 and 2011 are in a league of their own with 157 and 166 F/EF2+ tornadoes respectively. In 2019 there were “only” 56 EF2+ confirmed during the May volley. 2020 had 54 strong tornadoes despite featuring less than half the tornadoes of 2019 in the peak month.

Even with some expectations in mind, individual tornado outbreaks can make or break a peak month, and it seems likely that some longer-term shifts are ongoing thanks to climate change.

Top photo via NebraskaSC, May 20, 2019, in Mangum Oklahoma.

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Information lead and forecaster for the Washington Post's Capital Weather Gang.

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2 thoughts on “Peak tornado season is often April or May, but that’s not always the case

    1. I’m not affiliated with the writer of the article, but I think the colors are arbitrary (and probably unnecessary), where in the chart states with the same peak months are grouped by the same color.

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