Closer to the coast than it once was, and yet still fairly far north, the Katahdin region is subject to battering from both sides: hurricanes frequently slam into Massachusetts and tear upward into the rest of New England, while the Great Lakes region funnels winter and spring storms into the St. Lawrence Seaway and its nearest neighbors. The mountains sometimes catch and stall weather fronts, causing powerful thunderstorms to crash through the peaks.
As violent as this all sounds, there's still plenty of good weather to be had. Blue skies and puffy clouds lend a particular depth to the view of the waterways and islands from Katahdin's peaks. Temperatures in the lowlands vary from -20 C in the depths of winter to 50 C in the worst of the summer. The temperatures drop precipitously as the altitude rises; it is not uncommon to find one's breath misting at the caern in deep summer. Winter on the slopes of Katahdin is still vicious, even in the days of the Sun's Rage, and people are advised at all times of year not to walk on the Knife Edge if there is even a chance of bad weather -- there are high winds there on the best of days, and people have been swept off during storms, their bodies never to be found.