WASHINGTON — Before Jay Beagle took the ice for the Capitals in Game 3 against the Rangers on Monday, he stepped on a scale and noted his weight, to use later as a reference point.

Beagle played for only about 13 minutes, but he terrorized the Rangers, racing around, applying pressure, winning the majority of his face-offs. He scored the game’s only goal, hustling for the puck and banking it off two Rangers, as Washington took a 2-1 series lead in the Eastern Conference semifinals.

Beagle was sweating heavily. He was working hard, sure, but Verizon Center felt warmer than usual, probably because there was a high of 84 degrees outside that day.

After coming off the ice, he stepped on the scale again. He had lost about eight pounds.

This is the reality of playoff hockey. As the N.H.L. postseason continues into June, the weather warms, of course, and summer comes. Sometimes players have to battle dehydration, fatigue and subpar ice conditions, all in the most important games of their lives. This is widely accepted as a hazard of the job.