It has rained in Waynesburg on that day 111 out of the past 135 years.
Waynesburg Mayor Blair Zimmerman is three-for-three in hat bets since taking office, including one from Miss America 2009, Katie Stam, when it rained again last year.
He's challenging Houston Mayor Annise Parker because that city hosted a borough patrolman, Brian Tennant, and his family when Tennant needed several weeks of radiation treatments for his cancer this spring.
Waynesburg mayors have made 'Rain Day' bets with celebrities for years, including Donald Trump, actor Will Ferrell and Pittsburgh Steelers star Troy Polamalu.