It is extremely important that you eat and drink properly when cycling in extremes of temperature.
In Dubai, where riding in the summer means riding regularly in 50c temperatures, this is a major problem.
Eating is less of a concern than hydration, but you want to avoid dehydrators, like alcohol, in your food. You also want to watch what spices and additives are present in your food, like high salt content, but your standard diet as noted (High protein the night before, and carbs after a ride and assuming unsalted nuts and trail mix) should be fine to ensure energy. (Too much salt in one go can upset the stomach by drawing water into the gut, especially if you're already dehydrated. So it needs to be in small doses.)
Avoid sugary drinks, stick mainly with water, and electrolyte replacement drinks with low sugar content.
Desert survival expert Marjorie Woodruff recommends drinking a few ounces of water every 1o minutes if water is limited, and a minimum of 1 liter every 45 minutes if water is readily available. Electrolyte replacement s fairly essential, but can be accomplished far more inexpensively using a product like Elete Water because it can be carried easily, and a very small container is an effective add in to about 25 liters of water. It's mostly tasteless, but in our experience here in Dubai, very useful.
Proper clothing is essential. Cover your skin. Do not rely solely on sunscreens, as they do not prevent dehydration, although they are better than nothing. Better yet, do both.
Another essential in hot weather cycling, especially while touring, and deadly essential if touring unsupported is the ability to recognize and understand what is happening when you are affected by heat, and what it feels like.
This article from the Mayo Clinic has a pretty thorough examination of exercise in hot weather, and what the dangers and effect are.
How to avoid heat-related illnesses
When you exercise in hot weather, keep these precautions in mind:
Watch the temperature. Pay attention to weather forecasts and heat
alerts. Know what the temperature is expected to be for the duration
of your planned outdoor activity.
Get acclimated. If you're used to exercising indoors or in cooler
weather, take it easy at first when you exercise in the heat. As your
body adapts to the heat over the course of one to two weeks, gradually
increase the length and intensity of your workouts.
Know your fitness level. If you're unfit or new to exercise, be extra
cautious when working out in the heat. Your body may have a lower
tolerance to the heat. Reduce your exercise intensity and take
Drink plenty of fluids. Dehydration is a key factor in heat illness.
Help your body sweat and cool down by staying well hydrated with
Don't wait until you're thirsty to drink. If you plan to exercise
intensely or for longer than one hour, consider a sports drink instead
Sports drinks can replace the sodium, chloride and potassium you lose
through sweating. Avoid alcoholic drinks because they can actually
promote fluid loss.
Dress appropriately. Lightweight, loosefitting clothing helps sweat
evaporate and keeps you cooler. Avoid dark colors, which can absorb
heat. If possible, wear a light-colored, wide-brimmed hat.
Avoid midday sun. Exercise in the morning or evening, when it's likely
to be cooler outdoors.
If possible, exercise in shady areas — or do a water workout in a
Wear sunscreen. A sunburn decreases your body's ability to cool
Have a backup plan. If you're concerned about the heat or humidity,
stay indoors. Work out at the gym, walk laps inside the mall or climb
stairs inside an air-conditioned building. Understand your medical
risks. Certain medical conditions or medications can increase your
risk of a heat-related illness. If you plan to exercise in the heat,
talk to your doctor about precautions.
Heat-related illnesses are largely preventable.
By taking some basic precautions, your exercise routine doesn't have
to be sidelined when the heat is on.