You Have to Carry Much More Water to Ride in 110°F+ Temperatures
When temperatures are below 98.6°F, you may perspire less than 1 quart per day. But when the need for evaporative cooling kicks in, you perspiration rate can increase to 1.5 quarts PER HOUR. If you aren’t drinking 1.5 quarts per hour under extreme conditions, you will start becoming dehydrated. Your perspiration rate will decrease, you will feel hotter, your heart rate will increase, and your judgement will start to become clouded. If you are a competitive endurance rider, you can probably go at least 300 miles without stopping. If you are averaging 75 mph, that’s four hours. You may need to consume 6 quarts of water in that period of time when the temperature exceeds 110°F.
I carry an insulated 1-gallon cooler with a drinking tube attached when I know I will be riding long distances in hot weather. It was barely adequate for this trip because I deviated from my normal routine and purchased an extra bottle of water to drink during my fuel stops. On one leg, I made the mistake of starting with less than a full gallon and started experiencing the early signs of heat exhaustion. I felt much better after sitting in the shade for 10 minutes while consuming a full quart of bottled water.
Based on my personal experience and research, there is a world of difference between 100-105°F and 115°F in terms of how much water you need. A half quart per hour is more typical of what’s required near 100°F. You might even be able to run without water for several hours at about 100°F and make up the deficit by drinking at lot at your next fuel stop. But at 115°F, the level of dehydration you will be experiencing between fuel stops is excessive; you will definitely experience heat exhaustion and possibly heat stroke.
Why You Might Not Want to Be Wearing Shorts Under Your Riding Suit
Some popular bikes have “issues” with high levels of engine heat. My K1200GT makes the lower half of my legs warmer than on my K1200LT, but it’s never been a problem for me, until this trip. Air passing through the radiator on both the LT and GT exits at the side of the fairing just in front of the rider’s legs. On the LT, the hot air is blown far enough away from the bike that it does not impinge on the rider’s legs. On the GT, the fairing is not quite as wide and you can feel heat from the radiator on your lower legs. The heat I feel on the GT is clearly less that the heat I’ve felt riding other bikes, such as the FJR1300. But on this trip, the heat became a problem. I rode for a long stretch with a slight crosswind which increased the amount of radiator discharge that impinged on my right leg. It got very uncomfortable. When I stopped for the night, I discovered that I had second degree burns on the back of my right calf:
This wouldn’t have happened if I had been wearing long pants under my Aerostich. Under identical conditions, I did not get burned wearing blue jeans under the riding suit.
This problem showed up for the first time because the radiator discharge temperature is directly related to the ambient temperature. Although engines run hotter in hot weather, they actually discharge about the same amount of heat energy into the radiator. That heat energy raises the temperature of the radiator discharge the same amount that it does at lower ambient temperatures. At 100°F, the radiator discharge might be 140°F and it might get knocked down to 110°F before it impinges your leg. It feels very warm, but it won’t burn you. If the ambient is 15°F higher, you leg might be exposed to 125°F and you can eventually get burned if your leg isn’t insulated from the radiator discharge.
According to data from the National Burn Center, the time at temperature to cause a second degree burn is as follows:

113°F 1.7 hours
122°F 2 minutes
131°F 11 seconds
140°F 2 seconds

The only thing protecting you from being burned when your bare skin is exposed to ambient temperature of 113°F or higher is evaporative cooling and the cooling of the skin surface by blood flow. To be protected from radiator discharge temperatures in excess of 113°F, you need INSULATION between your skin and the hot air stream. What I painfully discovered is that the insulation provided by an Aerostich suit is not enough.
Indicators of heat stroke include
  • headache
  • dizziness
  • disorientation
  • hot, dry skin
  • sluggish
I just read an article on temperatures in cities versus temperatures outside of the city.  Tests have shown that on the same day, at the same time, temperatures in the city can be 20 degrees hotter, so make note of this when you travel into a city.
Ride safely and hydrate often,
 thanks to LIZ!