Coaches, referees, and parents share responsibility for managing the safety of the players and volunteers when it involves heat or cold stress. This topic is too involved and complex to present a detailed discussion on this page. Refer to the Safe Haven Certification Manual for guidance.
The referee's first duty is to the safety of the players. The referee is empowered to (and must) stop the game play at anytime/immediately due to a significant injury, including those related to heat and cold stress. The definition of significant injury is dependent on the age and conditions. The game play is stopped sooner/quicker for younger players whereas for older players it might be allowed to continue for a short time depending on the situation. Game durations can be adjusted by the Referee upon consultation with the Coaches due to extreme weather conditions, such as extreme heat or cold.
In cold weather, players are allowed to wear warm clothing UNDER their uniforms. Hats without brims (e.g., knit caps) and gloves are also allowed. Sweatshirts worn under a shirt are allowed if they do not have hoods. (In the Select season, rules are pickier about dress, but safety is more important than appearance.) The referee has the last say on what is allowed but should be biased on the side of safety. For more on cold weather safety, including how to deal with hypothermia, see this page.
In hot weather, referees must be very attentive to the effects of heat on players. Breaks and half-time periods can be lengthened somewhat, if needed, to allow for hydration and recuperation. Periods of play may be shortened. Worse case, games can be terminated early. In U16/19 games (and in younger-aged games, if needed), play may be formally stopped to allow for hydration and recuperation. In any case, games must end prior to the scheduled start time of the next game.
Hydration during games: See the USSF memo at this link.
Electrical storm safety
See details here.