multiple tornado reports

Red circles show where there was a report of a tornado on Wednesday

Wednesday's tornado outbreak in Indiana and Ohio could rank among the largest tornado days on record for the month of August
after a final confirmed number of tornadoes is determined.

Though surveys are ongoing to determine the actual tornado count, there were nearly three dozen reports of tornadoes for the day. That's a large number for August, and they were all confined in a small corridor from central Indiana to northwest Ohio.

As of Thursday early afternoon, seven tornadoes had been confirmed in Indiana by the National Weather Service, including an EF3 in Kokomo, Indiana.


One of the Most Tornadic August Days Since 1950?

The most tornadoes for a single calendar day during the month of August dating to 1950 was Aug. 29, 2005, when Hurricane Katrina spawned 40, according to a tweet by Ian Livingston, co-founder of ustornadoes.com. Four other tropical cyclones are in the top 10 for the largest number of tornadoes in a single August day.


The rest of August's largest tornado days are dominated by states in the Midwest.

Leading the pack for the Midwest, and ranking as the fifth most active tornado day during the month, is Aug. 19, 2009. That day had 30 tornadoes across parts of five states, including Indiana and Ohio.

If 20 tornadoes are confirmed from Wednesday, it would crack the top 10 for the largest number of tornadoes in a single August day across the U.S. dating to 1950.

On a state level, this may end up being one of the largest August tornado days on record in Ohio.

The National Weather Service in Wilmington, Ohio, says that the most number of tornadoes for an August calendar day in Ohio is 7 on Aug. 28, 2006.

For Indiana, if 12 tornadoes are confirmed in Indiana from Wednesday, it would rank in the top 10 list for the most tornadoes during an outbreak in the state.

The most August tornadoes in Indiana during a single event is 8 set earlier this month on Aug. 15. This beat the old record of 5 on Aug. 9, 1969. Wednesday's outbreak may beat that record from Aug. 15.

Where Are August Tornadoes Most Common?

August as a whole is not a huge tornado-producing month, averaging about 72 twisters over the last 20 years. This ranks as the sixth most tornadic month of the year, on average.

Average number of tornadoes per month 1995-2014.

Average number of tornadoes per month 1995-2014.
Tropical cyclones contribute to a significant number of the tornadoes we see in August, as illustrated by the list of the most tornadic days from Livingston above. About 17 percent of tornadoes during the month of August have been from tropical cyclones (1976-2005), according to severe weather expert Dr. Greg Forbes of The Weather Channel.

Although the probability of tornadoes is not particularly high in any one location of the United States, compared to say May or June, some areas are somewhat more favored than others.

The map below from NOAA shows the probability of tornadoes across the U.S. in late August.

tornado probabilities
© NOAA
Parts of the Midwest and Plains have slightly greater odds of tornadoes than most of the country. This is partially due to that region's proximity to stronger jet stream winds that are typically located closer to the Canadian border in summer.

In addition, there are slightly favored odds for tornadoes along the Gulf Coast and Florida from tropical storms and hurricanes.