Located in northeastern Illinois at the southwestern tip of Lake Michigan, Chicago's official geographic coordinates are 41°53′0″N, 87°39′0″W. It sits on the continental divide at the site of the Chicago Portage, connecting the Mississippi River and the Great Lakes watersheds. The city lies beside Lake Michigan and two rivers: the Chicago River in downtown and the Calumet River in the industrial far South Side, entirely or partially flow through Chicago. The Chicago Sanitary and Ship Canal connects the Chicago River with the Des Plaines River, which runs to the west of the city.

When Chicago was founded in the 1830s, most of the early building began around the mouth of the Chicago River. According to the U.S. Census Bureau, Chicago has a total area of 234.0 square miles (606.1 km²), of which 227.1 square miles (588.3 km²) is land and 6.9 square miles (17.8 km²) is water. The total area is 2.94% water.

The city has been built on relatively flat land; the average elevation of land is 579 feet (176 m) above sea level. The lowest points are along the lake shore at 577 feet (176 m), while the highest point at 735 feet (224 m) is in the landfill on the city's far south side (41°39′18″N,87°34′44″W).

Since the first recorded earthquake in 1804, Chicago has occasionally experienced earthquakes. More recently, an earthquake with an epicenter in Ottawa, Illinois, registering about 4.3 on the Richter scale shook some buildings in Chicago on June 28, 2004. This earthquake sparked worries that the New Madrid fault might become active again. An earthquake of 6 or higher in the Missouri Fault might cause moderate to high damage in Chicago.

Cityscape

The city’s urban context is organized within a grid pattern. The pattern is modified by the shoreline, the three branches of the Chicago River, the system of active/inactive rail lines, several diagonal streets (including Clybourn Street, Milwaukee, Lincoln, Elston, Archer, and Ogden Avenues), the expressways, and hundreds of bridges and viaducts. In addition, the baselines for numbering streets and buildings are State Street (for east-west numbering) and Madison (for north-south numbering). Street numbers begin at "1" at the baselines and run numerically in directions indicated to the city limits, with N, S, E, and W indicating directions. Chicago is divided into one-mile sections which ideally contain eight blocks to the mile, with each block's addresses ideally occupying a 100-number range. Even-numbered addresses are on the north and west sides of streets; odd-numbered address are on the south and east sides.

Since the first steel-framed high-rise building of the world was constructed in the city in 1885, Chicago has been known for the skyscraper. Today, many high-rise buildings are located in the downtown area, notably in the Loop and along the lakefront and the Chicago River. The three tallest buildings are the Sears Tower (also the tallest building in North America), the Aon Center, and the John Hancock Center. The rest of the city consists of low-rise buildings and single-family homes. There are clusters of industrialized areas, including the lakefront near the Indiana border, the area south of Midway Airport, and the banks of the Chicago Sanitary and Ship Canal.

Future building sites that will contribute to Chicago's skyline include Waterview Tower, 400 North Lake Shore Drive, and the Trump International Hotel and Tower.

Along Lake Shore Drive, parks line the lakefront. The most notable of these parks are Grant Park and Millenium Park, which border the east end of the Loop, Lincoln Park on the north side, and Jackson Park in the Hyde Park neighborhood on the south side. Interspersed within this system of parks are 31 beaches, a zoo and several bird sanctuaries, McCormick Place Convention Center, Navy Pier, Soldier Field, the Museum Campus, and a water treatment plant.

Pushed along by the national real estate boom in recent years, Chicago has seen an unprecedented surge in skyscraper construction, most notably in the area directly south (South Loop) and north (River North) of the Loop. This has been accompanied by a rapid gentrification of many parts of the city, as once-dormant areas become "hip" neighborhoods replete with an increased level of commercial services. An example is the west-side neighborhood Wicker Park.

Climate

Chicago, like much of the Midwest, has a climate that is prone to extreme, often volatile, weather conditions. The city experiences four distinct seasons. In July, the warmest month, high temperatures average 84 °F (29 °C) and low temperatures 63 °F (17 °C). In January, the coldest month, high temperatures average 29 °F (−2 °C) with low temperatures averaging 13 °F (−11 °C). According to the National Weather Service, Chicago's highest official temperature reading of 105 °F (40 °C) was recorded on July 24, 1934. The lowest temperature of −27 °F (−32 °C) degrees was recorded on January 20, 1985.

Chicago's yearly precipitation averages about 38 inches (965 mm). Summer is the rainiest season, with short-lived rainfall and thunderstorms more common than prolonged rainy periods. Winter is the driest season, with most of the precipitation falling as snow. Chicago's highest one day precipitation total was 6.49 inches (164 mm) which fell on August 14, 1987.