yes you can get dehydrated in freezing or cold or cool weather as well as hot, you just don't feel so thirsty when it is cooler. Unless it is pouring rain and cool, the air is generally drier when it is cool.

You can do a concentrated study of your sweat rate per mile by weighing yourself naked, gearing up, riding your average pace for as hour out and an hour back, ungear, weigh yourself again, subtract the second weight from the first to see how much weight you lost to sweat, add in 8 ounces for every 8 oz. equivalent of liquid you consumed and you will have your average sweat rate per hour for those particular weather conditions. Do it on several different days with different weather conditions, always on the same route, and you will have an idea of how much you should be drinking per hour.

My particular rate is between 12 and 18 oz per hour which works out to 2/3 a bottle of frs or water per hour. I alternate bottles and carry extra tubes of FRS so that I can buy plain water and mix a fresh batch on longer rides.

The bonk is insidious, and usually by the time you notice that you are bonking, you have tonconvince yourself that you don't have two flat tires and that the world is not spinning.

easiest thing to do is to stay ahead of it, even if it mean you have to stop and pee a bit more often.

marni