If you’ve ever driven up to a mountain pass, you know that the higher you climb, the colder it gets. But on clear, calm days, it can actually be colder in the valleys. That’s because under high pressure systems, cold air slides down mountain slopes and pools down below. In the Oregon Cascades, ridgeline temperatures have clocked in at 27 degrees Fahrenheit warmer than those in a valley 2,600 feet below. [More]