The weather listens to no one and does not plan around our schedule. So in St. John's, NL, they plan around the weather... for a holiday.
The first Wednesday in August is Regatta Day, a holiday. The only thing is, it depends on the weather.
If the weather is not favorable on that Wednesday, the holiday moves to a day when it will be favorable.
Since Regatta Day is a civic holiday in St. John's, this means that the weather actually determines whether or not workers have the day off – a matter sometimes complicated by late-night partying associated with the end of the George Street Festival the night before.
This has led to the coining of the term "Regatta Roulette" where people head to George Street Festival or party elsewhere the night before and hope the weather is nice enough for the Regatta (and the holiday) the next day.