New Hampshire is made up of three geographic areas: the coastal lowland in the southeast; the New England Uplands, covering most of the south and west; and the White Mountains (part of the Appalachian chain) in the north. During the last ice age, a huge ice sheet moved like a giant bulldozer across the state from the northwest to the southeast. As much as 400 feet (120 metres) of loose sand, silt, clay, and gravel were deposited in some areas, creating hills and mountains. The mountain passes of New Hampshire—Crawford, Dixville, Franconia, and Pinkham—were also carved by glacial action. The mountains are the most striking feature of New Hampshire’s landscape. There are about 1,500 mountains or hills in the state, including several peaks in the White Mountains higher than 5,000ft (1,500m). The best-known is Mount Washington, at 6,288ft (1,917m), which is the third highest peak in the country east of the Mississippi River.

The many lakes that dot the New Hampshire countryside were formed by the movement of glaciers during the last ice age. There are around 1,300 lakes and ponds in the state. The largest is Lake Winnipesaukee, which covers 70sq milesi (181sq km). New Hampshire has five main drainage basins. The largest is that of the Merrimack River, in the central part of the state. Second in size is the Connecticut River drainage basin, along the western border. The remaining waters flow into the Saco, Piscataqua, and Androscoggin rivers, also called the coastal rivers, as well as into several smaller streams. Near the coast are the nine rocky Isles of Shoals, three of which belong to New Hampshire.

New Hampshire has a changeable climate, with big differences in temperature from day to day and season to season. Summers are short and cool, and winters are long and cold. In winter temperatures may drop below 0°F (-18°C) for days at a time. Around 42in (1,070mm) of rain falls each year, along with about 50in (1,270mm) of snow along the coast and 100in (2,540mm) of snow in the northern and western parts of the state. The record low temperature, -46°F (-43°C), was set at Pittsburg on 28 January 1925; the all-time high, 106°F (41°C) at Nashua, 4 July 1911. The world-record wind speed (other than during a tornado) was set on Mt. Washington on 12 April 1934 - 231mph (372kph).