PHILADELPHIA — Dan Craig sleeps maybe four hours a night leading up to outdoor games. He only goes out to dinner because he can check the status of the ice on his phone.

“Your mind’s always going,” said Craig, the NHL’s vice president of facilities operations.

After staging outdoor games in a deep freeze (Edmonton) and summerlike warmth (Los Angeles), the NHL seems capable of taking hockey outside just about anywhere in the U.S. and Canada knowing the ice will be almost as good as the sheets found inside.

When the Flyers hosted the Penguins on Saturday night, it was the 27th NHL outdoor game since 2003. Next season’s Winter Classic is at the Cotton Bowl in Dallas, where the average high on Jan. 1 is 56 degrees (13.3 Celsius).

No worries, hockey fans.

“We put the parameters out there as into what we feel the challenges are going to be at a certain climate in a certain area and this is what we’re going to run up against,” said Craig, who has worked all but two outdoor games. “And if we have to go to get different equipment, we go get different equipment. If we need more staff, we just go get more qualified people to come in and give us a hand to make sure that everything works the way it’s supposed to.”

Weather is the biggest hurdle that can’t be controlled. It is instead managed by Craig, his son Mike, senior facilities operations manager Derek King and the 100-person crews that work each game. As he sat on the boards Thursday at Lincoln Financial Field, Craig pointed to the sky and acknowledged the swirling wind was on his mind.

Still, improved technology and techniques learned over the past 15 years have helped perfect the science and execution of making and maintaining outdoor ice.

“It seems like they’ve streamlined the process so they know how to react and how to handle different elements,” said Flyers winger James van Riemsdyk, a veteran of five outdoor games. “For the last few that I’ve been in, it’s all been pretty good. If you can start with that, that leads to a better product in the game.”

It starts with a 53-foot refrigeration truck that feeds coolant into aluminum trays set up on the field, and while indoor facilities have ice typically an inch or so deep, outdoor rinks go beyond 2 inches to protect the surface from the elements. Smaller Zambonis have less impact on the ice, and covering the surface with heat-reflecting insulation tarps helps. The ice can be monitored with sensors that provide real-time readings to a smartphone app.

The ideal ice temperature is 22 degrees (-5.5 Celsius), but all was fine in Denver in 2016 when the air temperature was 65 (18.3 Celsius) because officials can just turn the A/C up.

“When we’re monitoring the air temperature we’ll just make the sheet colder,” King said. “If we can keep it in the in the mid-40s, it would be great. But we’ve got a lot of control. We have a lot of control of the truck, so we can manipulate our temperatures on the sheet with the air temperature.”

Craig remembers the 2014 Winter Classic at Michigan Stadium in Ann Arbor: The snow shoveling started at 5 a.m. and never really stopped. The sun has been just as big an impediment — it delayed the 2012 Winter Classic in Philadelphia because the glare was considered a danger to players. The ice at the 2011 Heritage Classic in Calgary had to be covered because it was so cold there were worries the surface would crack, the most concerned Craig has ever been.

The tarps with air bubbles inside became a mainstay beginning in 2014 at Dodger Stadium to combat the Southern California sun as temperatures soared to almost 80 (26.7 Celsius) in the days before the game.