Williston sits on the open northern plains at roughly 600 metres elevation, and its climate is about as continental as it gets in the lower 48 states. Expect extremes in both directions. Winters are long and bitter — temperatures below −20 °C are routine from December through February, and blizzards can close roads for days at a stretch. Pack layers, plan for delays, and never start a long prairie drive in deteriorating weather without a full tank and emergency gear in the boot.
Summer arrives quickly and can be intense. July highs regularly hit 35 °C or above, and the wide-open sky offers little shade. The good news is that humidity stays low, so the heat is usually bearable in the morning and evening hours. This is the best window for visiting the historic sites: Fort Union and Fort Buford are at their most accessible from May through September, and the Missouri River recreation areas are genuinely pleasant on a warm afternoon.
Spring and autumn are brief but rewarding for travellers who catch them. May and September bring mild temperatures, smaller crowds, and the particular quality of light that the northern plains do so well — huge skies, long shadows, and a stillness that is hard to find anywhere closer to a city.