Armonk is a hamlet and census-designated place (CDP) in the town of North Castle, New York, located in Westchester County.
As of the 2010 census, Armonk's CDP population was 4,330 and it has a total area of 6.1 square miles (15.7 km2), of which 6.0 square miles (15.5 km2) is land and 0.077 square miles (0.2 km2), or 1.54 percent, is water.
The corporate headquarters of IBM are situated in Armonk.
Situated 11 miles from the coast in the Southeastern corner of New York, Armonk shares a border with Connecticut. The landscape is hilly and forested, with a mean elevation of 387 feet, and is home to the highest point in Westchester County with an elevation of 1,396 feet.
Armonk has a humid subtropical climate (Type Cfa) with cold, wet winters with occasional snow and hot, humid summers. Precipitation is plentiful, with the winter months receiving more precipitation than the summer months. Snowfall varies a lot from year to year, some years seeing just a few inches while others may see upwards of 35 inches, but average snowfall is 28 inches. Winter precipitation comes mainly in the form of coastal storms that bring rain, snow and wind to New England and the Mid-Atlantic. Summer brings mostly stable, hot weather with 18 days per summer reaching 90º. Summer is relatively dry but not rainless, with scattered thunderstorms and the risk of a rare tropical storm in August and September. Spring and fall are transition seasons with moderate temperatures and moderate precipitation.