I know the rule of thumb is a 24 oz bottle per hour and that may work for some people in some climates but not for me. Did a test today.
Before I started my ride this morning I dressed in my normal gear, filled my 70 oz camelback and tanked up by drinking a a 24 oz gatorade. I then weighed myself with full camelback, about 3 pounds of Shimano sandals and biking clothes: 210.8 pounds.
The ride: The temps ran from 82 to 88 degrees (8:30-10:30 AM) with a dew point of 72 degrees (humid as h***). The ride was 30.01 miles in 1:50 for a ride average of 16.4 mph, wasn't pushing, just trying to duplicate an average ride for me. There was a modest amount of climbing at 470 feet and a 7 mph wind.
BTW: I drained the gatorback during the ride.
When I got back, went straight in a weighed in the same configuration (camelback + sandals + biking clothes) as earlier: 203.0, or 7.8 pounds less than where I started. Should have thought about it but one variable that I didn't take into account was the weight of the moisture in my shorts and shirt, it was significant. One gallon of water weights 8.3 pounds
Conclusion: Today at least, if I had restricted myself to 24 oz/hour, I would have been BADLY dehydrated. Correcting for the moisture in the clothing, I sweated out very close to or slightly over a gallon of water in less than two hours. This is very close to 3-24 oz bottles of water per hour.
The Florida humidity is often high enough that there is very little evaporative cooling.