Even while the Blues play on the West Coast until Monday, three massive dehumidifiers are temporarily bolted to the Scottrade Center roof, running around the clock and sucking water from 2,000 tons of air above the ice.

Mid-May hockey. Who knew?

Doug Waugh, senior director of building operations for Scottrade, said the units "are basically very large dryers."

"They run on natural gas and they take the chilled air from the air-conditioning units and cool it before it goes out" into the arena, Waugh said.

To understand why the Blues and most every other team in the second round of the Stanley Cup playoffs rented these dryers, know this:

The ideal conditions for hockey is a building temperature of 60 degrees and 40 percent humidity; the National Hockey League requires the venue to register at no more than 65 degrees and 44 percent humidity.

"This is all aimed at keeping the ice from getting slushy," Waugh said. Along with better skating, the colder ice and dry air reduces the chance of rink "fog" creeping in.

And since Waugh and other building bosses strive deep down to meet not just the NHL standard but the "60-40" ideal, they all rent these dryers.