May Tornadoes
May averages 270 tornadoes in the US - more than any other month. Great Plains peak. Notable May events include Joplin 2011, Moore 1999, El Reno 2013, Greensburg 2007.
Why May Is the Peak Month
By May, the US atmosphere reaches maximum tornado potential in the Great Plains:
- Gulf moisture is at peak levels - dew points routinely 65-70°F
- Jet stream still strong - producing extreme wind shear
- Surface heating maximizes - producing extreme atmospheric instability
- Dryline positioned over Texas/Oklahoma - providing daily triggers for supercells
These four factors combine to produce the most consistently favorable tornado atmosphere anywhere on Earth. May 2011 saw 542 tornadoes in a single month - one of the highest monthly totals ever recorded.
Notable May Tornado Events
- May 3, 1999 Bridge Creek-Moore F5 - 36 killed, 301 mph world record wind
- May 22, 2011 Joplin EF5 - 158 killed, deadliest modern US tornado
- May 20, 2013 Moore EF5 - 24 killed, Plaza Towers Elementary
- May 31, 2013 El Reno - widest ever recorded (2.6 mi), TWISTEX deaths
- May 4, 2007 Greensburg EF5 - first-ever EF5
- May 11, 1953 Waco F5 - 114 killed, created the warning system
- May 25, 2008 Parkersburg EF5 - second-ever EF5
- May 4, 1991 Andover F5 (day after outbreak) - Golden Spur
- May 27, 1997 Jarrell F5 - most extreme damage ever
- May 25, 1955 Udall F5 - 80 killed at night
May vs. April - Which Is Deadlier?
Historically, April kills more people per year despite May having more tornadoes. Why: April concentrates outbreaks in the Deep South where population density and nighttime tornado rates are higher. May outbreaks tend to spread across the more sparsely populated Great Plains.
Exception: May 2011 killed 178+ Americans due to Joplin (158) plus other events. May 2013 killed 47 with Moore and El Reno. When May outbreaks strike major cities, the death toll rivals April.
The Great Plains May Corridor
Peak May tornado activity concentrates in a corridor running from north Texas through Oklahoma, Kansas, Nebraska, and into Iowa. This corridor - sometimes called the "spring supercell alley" - produces roughly 40% of all US May tornadoes.
Individual state peaks in May:
- Oklahoma: May is by far the peak month
- Kansas: May-June split as peak
- Texas: May is peak in the Panhandle; April in the north
- Nebraska: May-June split
- Iowa: June is actually the peak, with May close behind
Late May Extremes
The last week of May has produced some of the most historically significant US tornado events:
- May 25, 1955 - Udall, KS F5 (80 killed)
- May 27, 1896 - St. Louis F4 (255 killed)
- May 27, 1997 - Jarrell F5
- May 22, 2011 - Joplin EF5
- May 24, 2011 - El Reno-Piedmont EF5
- May 25, 2008 - Parkersburg EF5
- May 31, 2013 - El Reno (widest ever)
Meteorologists have noted this "late May peak" for years - a period of consistently extreme atmospheric setups over the central US.
Preparing for May
- Household tornado drill in April, review results in early May
- NOAA weather radio tested and batteries fresh
- Insurance policy reviewed for wind/hail deductible
- Shelter plan communicated to everyone in the household
- Pay attention to SPC forecasts - especially "Enhanced" or "Moderate" risk days
Try the interactive simulator
Place an EF0–EF5 tornado anywhere in the world and see modeled fatalities, structural damage, and economic loss based on real census data.
Launch simulator →Try the interactive simulator
Place an EF0–EF5 tornado anywhere in the world and see modeled fatalities, structural damage, and economic loss based on real census data.
Launch simulator →