This is especially true for long approaches, where one may be climbing several days after having last heard the official forecast. Some confidence about the weather's prospects is much better than just hoping for the best. There's no substitute for familiarity. Along the same lines, probably the greatest danger the average hiker and climber faces is lightning. Such situations can fairly rapidly escalate to the well known phenomena of hair standing on end and the landscape around buzzing with static discharge.
Lightning is notoriously unpredictable and can strike virtually anywhere.
In other words, do not think that just because you're a relatively inconspicuous object down in a valley that you can't be hit. Most accidents occur during descents. I know there are some reports out there that don't support this proposition, but I think their data comes more from real climbing situations than sport mountaineering. Remember, when you've made it to the top you're only half way from your ultimate objective. It's almost always harder to climb down things than to climb up them.