In Short
Although the climb to the top of Mount St. Helena is full of wildflowers and beautiful, spiraling trails, it can be long and it can be hot. That's why spring and autumn, when the temperature is mild, are the favored seasons for most hikers. Keep in mind, there are actually two summits, with two different trails leading up to them. Figure out beforehand which one you want to climb, since one trail is 10 miles round trip and the other a mere six and a half.