Some good comments/suggestions here. I am new to eastern Kansas and the high humidity but worked as a paramedic and ran a paramedic service for years and was involved in athletic activities for myself that involved calculating water and electrolyte consumption. Here is a website that has several helpful hints: http://www.gatorade.com/default.aspx...eries_article1
The other fluid I used a lot was G2, it has half the sugar as Gatorade - they have a low calorie version also but still has the sodium and potassium and some carbohydrates needed. That combined half and half with water or just a bottle several times a day along with plenty of water can help keep the balance. If all you drink is water you can become depleted on the sodium and potassium. I think what has been mentioned here as to heat problems is mostly along the lines of heat exhaustion, not heat stroke. Heat Stroke is an immediate 911 call and is life threatening. Heat exhaustion means stop working, get fluids and shade and no work for the rest of the day. Heat exhaustion is the road to heat stroke if you don't treat it early. For you guys who have no choice but to keep working all day it sounds like you are aware of what you have to do but there is no harm in researching this further on the internet via the medical websites.
It is a fact that most athletes and hot weather workers do not drink enough fluids. Make sure your urine is not dark yellow and stays a lighter color. I work around a 5 acre property and have a little fanny pack, and a CamelBak that has a water bottle holder and nothing else. Some of you may use the CamelBak, etc. These are great and can hold a lot of water and you can drink as you work. That way I still drink when I'm on the tractor and don't want to take time to get to the house or vehicle for water and can refill when I do. Thanks for reminding me of this issue in the hot and humid climate that I just moved to.