The Geology of New Hampshire is relatively similar to the rest of the New England region.
The state is bounded by Quebec, Canada, to the north and northwest; Maine and the Atlantic Ocean to the east; Massachusetts to the south; and Vermont to the west. New Hampshire's major regions are the Great North Woods, the White Mountains, the Lakes Region, the Seacoast, the Merrimack Valley, the Monadnock Region, and the Dartmouth-Lake Sunapee area. New Hampshire has the shortest ocean coastline of any U.S. coastal state, with a length of 18 miles (29 km),  sometimes measured as only 13 miles (21 km).  New Hampshire was home to the rock formation called the Old Man of the Mountain, a face-like profile in Franconia Notch, until the formation disintegrated in May 2003.
The White Mountains range in New Hampshire spans the north-central portion of the state, with Mount Washington the tallest in the northeastern U.S. – site of the second-highest wind speed ever recorded  – and other mountains like Mount Madison and Mount Adams surrounding it. With hurricane-force winds every third day on average, over 100 recorded deaths among visitors, and conspicuous krumholtz (dwarf, matted trees much like a carpet of bonsai trees), the climate on the upper reaches of Mount Washington has inspired the weather observatory on the peak to claim that the area has the "World's Worst Weather". 
In the flatter southwest corner of New Hampshire, the landmark Mount Monadnock has given its name to a class of earth-forms – a monadnock – signifying, in geomorphology, any isolated resistant peak rising from a less resistant eroded plain.
Major rivers include the 110-mile (177 km) Merrimack River, which bisects the lower half of the state north-south and ends up in Newburyport, Massachusetts. Its tributaries include the Contoocook River, Pemigewasset River, and Winnipesaukee River. The 410-mile (660 km) Connecticut River, which starts at New Hampshire's Connecticut Lakes and flows south to Connecticut, defines the western border with Vermont. The state border is not in the center of that river, as usually the case, but at the low-water mark on the Vermont side; meaning that the entire river along the Vermont border (save for areas where the water level has been raised by a dam) lies within New Hampshire.  Only one town – Pittsburg – shares a land border with the state of Vermont. The "northwesternmost headwaters" of the Connecticut, now known as Halls Stream, define Canada's border with New Hampshire.
The Piscataqua River and its several tributaries form the state's only significant ocean port where they flow into the Atlantic at Portsmouth. The Salmon Falls River and the Piscataqua define the southern portion of the border with Maine. The Piscataqua River boundary was the subject of a border dispute between New Hampshire and Maine in 2001, with New Hampshire claiming dominion over several islands (primarily Seavey's Island) that include the Portsmouth Naval Shipyard. The U.S. Supreme Court dismissed the case in 2002, leaving ownership of the island with Maine.
The largest of New Hampshire's lakes is Lake Winnipesaukee, which covers 71 square miles (184 km2) in the east-central part of New Hampshire. Umbagog Lake along the Maine border, approximately 12.3 square miles (31.9 km2), is a distant second. Squam Lake is the second largest lake entirely in New Hampshire.
New Hampshire has the shortest ocean coastline of any state in the United States, approximately 18 miles (29 km) long.  Hampton Beach is a popular local summer destination. About 7 miles (11 km) offshore are the Isles of Shoals, nine small islands (four of which are in New Hampshire) known as the site of a 19th-century art colony founded by poet Celia Thaxter, and the alleged location of one of the buried treasures of the pirate Blackbeard.
It is the state with the highest percentage of timberland area in the country.  New Hampshire is in the temperate broadleaf and mixed forests biome. Much of the state, in particular the White Mountains, is covered by the conifers and northern hardwoods of the New England-Acadian forests. The southeast corner of the state and parts of the Connecticut River along the Vermont border are covered by the mixed oaks of the Northeastern coastal forests. 
The northern third of the state is locally referred to as the "north country" or "north of the notches", in reference to White Mountain passes that channel traffic. It contains less than 5% of the state's population, suffers relatively high poverty, and is steadily losing population as the logging and paper industries decline. However, the tourist industry, in particular visitors who go to northern New Hampshire to ski, snowboard, hike and mountain bike, has helped offset economic losses from mill closures.
New Hampshire experiences a humid continental climate ( Köppen climate classification Dfa in southern areas and Dfb in the north), with warm, humid summers, cold, wet winters, and uniform precipitation all year. The climate of the southeastern portion is moderated by the Atlantic Ocean and averages relatively milder and wetter weather, while the northern and interior portions experience cooler temperatures and lower humidity. Winters are cold and snowy throughout the state, and especially severe in the northern and mountainous areas. Average annual snowfall ranges from 60 inches (150 cm) to over 100 inches (250 cm) across the state. 
Average daytime highs are in the mid 70s°F to low 80s°F (around 24–28 °C) throughout the state in July, with overnight lows in the mid 50s°F to low 60s°F (13–15 °C). January temperatures range from an average high of 34 °F (1 °C) on the coast to overnight lows below 0 °F (−18 °C) in the far north and at high elevations. Average annual precipitation statewide is roughly 40 inches (100 cm) with some variation occurring in the White Mountains due to differences in elevation and annual snowfall. New Hampshire's highest recorded temperature was 106 °F (41 °C) in Nashua on July 4, 1911, while the lowest recorded temperature was −47 °F (−44 °C) atop Mount Washington on January 29, 1934. Mount Washington also saw an unofficial −50 °F (−46 °C) reading on January 22, 1885, which, if made official, would tie the all-time record low for New England (also −50 °F (−46 °C) at Big Black River, Maine, on January 16, 2009, and Bloomfield, Vermont on December 30, 1933).
Extreme snow is often associated with a nor'easter, such as the Blizzard of '78 and the Blizzard of 1993, when several feet accumulated across portions of the state over 24 to 48 hours. Lighter snowfalls of several inches occur frequently throughout winter, often associated with an Alberta Clipper.
New Hampshire, on occasion, is affected by hurricanes and tropical storms although by the time they reach the state they are often extratropical, with most storms striking the southern New England coastline and moving inland or passing by offshore in the Gulf of Maine. Most of New Hampshire averages fewer than 20 days of thunderstorms per year and an average of two tornadoes occur annually statewide. 
The National Arbor Day Foundation plant hardiness zone map depicts zones 3, 4, 5, and 6 occurring throughout the state  and indicates the transition from a relatively cooler to warmer climate as one travels southward across New Hampshire. The 1990 USDA plant hardiness zones for New Hampshire range from zone 3b in the north to zone 5b in the south. 
From "The New Hampshire Economic and Labor Market Information Bureau". Archived from the original on January 11, 2008. Retrieved June 16, 2014.
While New Hampshire, along with the rest of New England, does not frequently experience earthquakes, it has experienced several in history and has been affected by some of the larger events that were centered in the Saint Lawrence rift system in Canada. One of these was the 1663 Charlevoix earthquake that was centered near the Quebec–Maine border, the magnitude of which has since been estimated at 7.3–7.9. In 1727, Newbury, Massachusetts, experienced a damaging earthquake that shook New Hampshire also. The 1755 Cape Ann earthquake, estimated magnitude 5.5–6.0, also shook most or all of New Hampshire. On November 9, 1810, Exeter experienced an estimated intensity VI (Strong) tremor. It was accompanied by an unusual noise like an explosion, and broke windows in Portsmouth. Concord, the capital, experienced a series of shocks between 1872 and 1891. One earthquake was felt in late 1872, lasting ten seconds in Concord, and was felt in Laconia and other towns to the north. Ten years later, another tremor was strongest in Concord, although Dover and Pittsfield reportedly had buildings shaken. On November 23, 1884, a light shock was followed fifteen minutes later by a severe earthquake in Concord. The second shock was felt in Massachusetts, Connecticut, and eastern New York. Concord's last tremor in that period was mild and was reported in Cambridge and Melrose, Massachusetts.
Southeastern New Hampshire and Maine experienced an earthquake in 1925. Dishes and goods were jostled from shelves in Ossipee, Tuftonboro, and Effingham Falls. In 1929 the Grand Banks of Newfoundland (800 miles (1,300 km) to the east) experienced a magnitude 7.2 earthquake and New Hampshire felt minor effects. In 1935, a 6.25 earthquake centered in Timiskaming, Ontario, 500 miles (800 km) away, was felt in an area of over 2,500,000 square kilometers (970,000 sq mi), and some places in New Hampshire experienced Mercalli Intensities as high as V (Moderate). Ossipee Lake was the site of two moderate earthquakes in December 1940. The quakes were felt in all six New England states, as well as parts of New Jersey and Pennsylvania. In the epicentral area, a large number of aftershocks happened. One observer counted over 120 aftershocks through January 31, 1941. 
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- Filipov, David (January 31, 2010). "Record blown away, but pride stays put: N.H. summit's claim to nasty weather intact". The Boston Globe. Retrieved February 9, 2010.
- "Mount Washington...Home of the World's Worst Weather". Mt. Washington Observatory. Retrieved March 22, 2010.
- VERMONT v. NEW HAMPSHIRE 289 U.S. 593 (1933)
- "New Hampshire Water Resources Primer, Chapter 6: Coastal and Estuarine Waters" (PDF). NH Dept. of Environmental Services. Retrieved April 11, 2011.
- "USDA report: "Tree and impervious cover in the United States (2012)"" (PDF).
- Olson, D. M, E. Dinerstein; et al. (2001). "Terrestrial Ecoregions of the World: A New Map of Life on Earth". BioScience. 51 (11): 933–938. doi: 10.1641/0006-3568(2001)051[0933:TEOTWA]2.0.CO;2. Archived from the original on October 14, 2011.
- Dellinger, Dan (June 23, 2004). "Snowfall — Average Total In Inches". NOAA. Archived from the original on February 19, 2002. Retrieved May 25, 2007.
- "Annual average number of tornadoes 1953–2004". NOAA. Retrieved May 25, 2007.
- "2006 arborday.org Hardiness Zone Map". National Arbor Day Foundation. Retrieved May 25, 2007.
- "New Hampshire USDA Plant Hardiness Zone Map". Retrieved November 15, 2010.
- "New Hampshire". Earthquake.Usgs.Gov. US Geological Survey Earthquake Hazards Program. Archived from the original on 2009-12-15.