People will slow down and make mistakes as the day drags on and the cold gets to the players.
Players get tired from playing. But if you have ever had some good exercise on a cold day, you would realize that the cold actually works to your advantage. In reality, hot days are much worse for staying alert and hydrated than are cold days. This whole weather issue is blown way out of proportion. Because, of course,
the coldest winter I ever spent was a summer in San Francisco
Mark Twain (sort of)