Hey. I find that my schedule is open late afternoon during the heat of the day, which for me means 95 degrees and humidity of 65 or so. . .Should I be doing my very hard interval workouts during this time or move them to early morning or late afternoon when it will be cooler? Thoughts in general on training during this type of heat. . .
Weigh yourself before your ride, drink a lot and then weigh yourself after. The difference is mostly the water you lost. Water weighs 1g / ml small bottle = 500ml -> .5kg = 1.1lb or a large bottle = 750ml or 1.65 lb.
Next ride take more or find a stop on your ride to refill. Start drinking as soon as you start your ride, don't wait until you are thirsty. If you do the above scale thing you can estimate how much water you should drink per hour.
The only thing I might add to that is to before you add your hard intervals, be sure you're acclimatized to that type of heat. That would kill me since I'm in the Nortwest and not used to that type of temp. Try it a few times and build each time and see how your body reacts to it. like stated above, be sure to get plenty of liquids and salts...