Forget Mayweather vs. McGregor. The real summer showdown may happen in the U.S. equity market: a battle between a seemingly impervious stretch of calm and the historically chaotic month of August.
August has brought the biggest monthly jumps in the VIX on record, with the gauge averaging a 12 percent climb over its 31 days, according to data compiled by Bloomberg going back 20 years.
The seasonal pattern also shows up in daily market moves, with more one-day swings of 1 percent or more in the Standard & Poor's 500 Index than in all but one other month since 1950, according to S&P Dow Jones data compiled by Sam Stovall. Only October sees more.
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"Crazy stuff happens in August," Michael Block, chief strategist at Rhino Trading Partners LLC in New York, wrote in a note to clients Tuesday. "Fair game, given all the choppiness and cross-currents and how successful punters have been selling volatility over and over again. That goes really well until it blows up yet again."
Summer swings aren't exclusive to stocks. A Bank of America Merrill Lynch index tracking Treasury market volatility boasts the second-highest monthly average in August, according to data compiled by Bloomberg. In the past 20 years, the index climbed an average 8.1 percent during the month.