Williston is located at 48°7'59" North, 103°37'59" West (48.133333, -103.633056).
According to the United States Census Bureau, the city has a total area of 7.04 mi2 (18.23 km2). 6.97 mi2 (18.06 km2) of it is land and 0.07 mi2 (0.17 km2) of it is covered by water. The total area is 0.93% water.
Williston is located in the Central Standard Time (CST) timezone, GMT-06:00. It observes Daylight Saving Time (DST).