page_title: Iowa
section_title: Climate
hierarchical_section_title: Iowa / Climate
caption_attribution_description: English: Iowa annual fainfall, in inches, created in ESRI ArcMap 9 from ISU-GIS- REF data, utimately from Iowa DNR and state climatologist data.
context_page_description: Iowa is a state in the Midwestern United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the east and southeast, Missouri to the south, Nebraska to the west, South Dakota to the northwest, and Minnesota to the north.
  In colonial times, Iowa was a part of French Louisiana and Spanish Louisiana; its state flag is patterned after the flag of France. After the Louisiana Purchase, people laid the foundation for an agriculture-based economy in the heart of the Corn Belt.
  In the latter half of the 20th century, Iowa's agricultural economy made the transition to a diversified economy of advanced manufacturing, processing, financial services, information technology, biotechnology, and green energy production. Iowa is the 26th most extensive in land area and the 30th most populous of the 50 U.S. states. The state's capital, most populous city, and largest metropolitan area fully located within the state is Des Moines. A portion of the larger Omaha, Nebraska, metropolitan area extends into three counties of southwest Iowa.
context_section_description: Iowa has a humid continental climate throughout the state (Köppen climate classification Dfa) with extremes of both heat and cold. The average annual temperature at Des Moines is 50 °F (10 °C); for some locations in the north, such as Mason City, the figure is about 45 °F (7 °C), while Keokuk, on the Mississippi River, averages 52 °F (11 °C). Snowfall is common, with Des Moines getting about 26 days of snowfall a year, and other places, such as Shenandoah getting about 11 days of snowfall in a year.
  Spring ushers in the beginning of the severe weather season. Iowa averages about 50 days of thunderstorm activity per year. The 30-year annual average Tornadoes in Iowa is 47. In 2008, twelve people were killed by tornadoes in Iowa, making it the deadliest year since 1968 and also the second most tornadoes in a year with 105, matching the total from 2001.
  Iowa summers are known for heat and humidity, with daytime temperatures sometimes near 90 °F (32 °C) and occasionally exceeding 100 °F (38 °C). Average winters in the state have been known to drop well below freezing, even dropping below −18 °F (−28 °C). Iowa's all-time hottest temperature of 118 °F (48 °C) was recorded at Keokuk on July 20, 1934, during a nationwide heat wave; the all-time lowest temperature of −47 °F (−44 °C) was recorded at Washta on January 12, 1912.
  Iowa has a relatively smooth gradient of varying precipitation across the state, with areas in the southeast of the state receiving an average of over 38 inches (97 cm) of rain annually, and the northwest of the state receiving less than 28 inches (71 cm). The pattern of precipitation across Iowa is seasonal, with more rain falling in the summer months. Virtually statewide, the driest month is January or February, and the wettest month is June, owing to frequent showers and thunderstorms, some of which produce hail, damaging winds and/or tornadoes. In Des Moines, roughly in the center of the state, over two-thirds of the 34.72 inches (88.2 cm) of rain falls from April through September, and about half the average annual precipitation falls from May through August, peaking in June.
caption: Iowa annual rainfall, in inches
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