Candy-making is a fiddly process and sometimes, the weather outside can affect the outcome. For example, if the weather is humid, the candy may or may not set and harden properly. You always have to be careful about cooking temperatures, and make *sure* your candy thermometer is accurate. You can test it by bringing water to a full, rolling boil, and seeing if it reads 212 degrees Fahrenheit.
I've found the weather equation to be especially critical when making fudge or divinity candy. In general, the best weather for these candies is cold, clear, winter weather when the humidity is low.
A club aluminum saucepan is a good choice for a candy pan. These are usually heavy-duty, good quality pots that will withstand an unbelievable amount of abuse that candy making entails. Also, for me, a wooden spoon is absolutely imperative for making candy. They don't conduct heat and they won't scratch a pan. A silicone spatula is also a helpful tool, since the silicone can withstand the heat with ease.