You need to be willing to train in all conditions. This is probably the hardest part about training for most people as it’s uncomfortable. You have to get comfortable at being uncomfortable. Practice running in the rain when the trails are sloppy and your feet are soaking wet. You can learn a lot during these runs and what changes you might need to make with gear. At some point, you will experience similar conditions in a race and it’s better to be prepared. Do you have the right shoes or socks on? Should you have dressed differently? Do you begin to chafe as a result? The more prepared you are the easier it becomes and you will begin to appreciate the experience. There is also a sense of achievement and satisfaction when you figure out what works.
Dealing with the heat and humidity is a biggie for us in southeast Texas. You want to learn how to train safely and effectively in the heat. What does it take to cool your body? I once thought stripping down to only running shorts was the key, but I have figured out that I am better off with wet clothing including a shirt, arm sleeves, hat, and a soaking wet buff around my neck.