Few things ruin a ride worse than getting soaked in a downpour while you're still miles from any shelter. One thing that is worse: getting soaked in a downpour when it's cold out. Of course, storms can materialize seemingly out of nowhere and you can't always call them. But for the most part, you can plan ahead what time of year will offer the best temperatures and least precipitation for an adventure cycling trip. Weather radar available today can show you at a glance if clouds are menacing your area and you should stick close to town, or if it's instead a clear and beautiful day, ripe for racking up the miles.
Another meteorological consideration: wind. On a bicycle, wind poses a powerful force to reckon with, especially if the bike is loaded down with stuff and that big sail known as your torso. Few people seem to mind wind at their backs. But a strong-blowing headwind can suck the fun right out of an otherwise pleasant trip leg. A headwind literally saps your energy, since you must work harder to overcome it and maintain forward speed. That's why when you're checking the weather, you also want to check the prevailing wind direction and speed.