When it's hot outside it's fairly obvious that you need to hydrate and drink enough with electrolytes to keep you pedaling strong.
Keep in mind that the same general rules of hydration apply in the cooler weather - If you're exercising for up to 1 hour, you can rehydrate with water alone. However, after an hour, add electrolytes and carbohydrates.
We Roundabout Century riders will be cycling for more than an hour so be sure to hydrate with your electrolyte mix and eat plenty of carbohydrates to keep you pedaling strong. For more info, see this article 8 Tips for Hydrating in Cold Weather from active.com.