My boat was glassed last summer in Jupiter, Florida. Think 85 - 90 degree days with 80 - 100% humidity. While most of my glassing was done using standard cure system 3 epoxy, it was very helpful to have slow cure epoxy available for the large area laminations. When you try to wet out a full deck or hull the standard cure epoxy sets up way too fast. I also learned not to epoxy in the morning. As the day heats up, any air entrained in the epoxy mixture expands, providing neat little epoxy bubbles which you then get to sand out. (think bubblegum bubbles). I did not note any humidity related effects or problems with the System Three.

Glass work with expoxy isn't hard, but having a slow setting epoxy during hot weather really helps quite a bit, and is well worth the cost of the extra hardener. I used manufacturer supplied pumps in my standard hardener and resin bottles, with a squeeze ketchup bottle full of slow set hardener for custom blends. Using medical dosing cups to mix each batch of epoxy, you can tailor the working time of each mix for the job you have to do - slow blends for large area laminations, fast blends for smaller jobs like fairing. Best of luck.