Thirsty? You may already be dehydrated. Thirst is always an adequate indicator of hydration. Some other signs of dehydration include decreased frequency of urination, headache and grouchiness.
It is important to drink around 16-20 ounces both before and after exercise, or, according to the American College of Sports Medicine, 4-8 ounces of fluid for every 15-20 minutes of activity. Try to keep your drinks slightly cooler than the air temperature, this may help speed their exit from your stomach, and make them taste better, which may affect how much you are willing to drink. Some people believe you cannot get dehydrated in cold weather. Not true. You can, and you will! The same rules apply for warm and cold weather, although you will probably dehydrate faster, and possibly notice it more in the warmer months.