Is it dangerous to drink too much water right after intense exercise?

Yes: During exercise, water is the best fluid replenisher for most individuals, although sports drinks help replace lost electrolytes during high intensity exercise exceeding 45 to 60 minutes. Individuals who sweat profusely during exercise and whose sweat contains a high amount of sodium should choose sports drinks and ensure that their diet contains adequate sodium to prevent water intoxication.

How much is too much: Depending on how long and how intensely and the conditions in which you exercised you lose a lot of water from your body.An averaged sized person can lose up to 2 liters[128oz or about 2 quarts] of water for the first hour or then a little less for each aditional hour in hot enviroment. You need to replace what you lose and you probably can safely double that amount. The timing should not matter.