Climate of Minnesota
has a humid continental climate, with hot summers and cold winters. Minnesota's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, with each of the four seasons having its own distinct characteristics. The area near Lake Superior in the Minnesota Arrowhead region experiences weather unique from the rest of the state. The moderating effect of Lake Superior keeps the surrounding area relatively cooler in the summer and warmer in the winter, giving that region a smaller yearly temperature variation. On the Köppen climate classification, much of the southern third of Minnesota—roughly from the Twin Cities region southward—falls in the hot summer zone, and the northern two-thirds of Minnesota falls in the warm summer zone.
Winter in Minnesota is characterized by cold temperatures. Snow is the main form of winter precipitation, but freezing rain, sleet, and occasionally rain are all possible during the winter months. Common storm systems include Alberta clippers or Panhandle hooks; some of which develop into blizzards. Annual snowfall extremes have ranged from over in the rugged Superior Highlands of the North Shore to as little as in southern Minnesota. Temperatures as low as have occurred during Minnesota winters. Spring is a time of major transition in Minnesota. Snowstorms are common early in the spring, but by late-spring as temperatures begin to moderate, the state can experience tornado outbreaks, a risk which diminishes but does not cease through the summer and into the autumn.
In summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north. These humid conditions initiate thunderstorm activity 30–40 days per year. Summer high temperatures in Minnesota average in the mid-80s F in the south to the upper-70s F in the north, with temperatures as hot as possible. The growing season in Minnesota varies from 90 days per year in the Iron Range to 160 days in southeastern Minnesota. Tornadoes are possible in Minnesota from March through November/December, with at least one recording of a tornado in December in Hartland Minnesota. The peak tornado month is June, followed by July, May, and August. The state averages 27 tornadoes per year. Average annual precipitation across the state ranges from approximately in the southeast to in the northwest. Autumn weather in Minnesota is largely the reverse of spring weather. The jet stream—which tends to weaken in summer—begins to revive, leading to a quicker changing of weather patterns and an increased variability of temperatures. By late October and November, these storm systems become strong enough to form major winter storms. Autumn and spring are the windiest times of the year in Minnesota.
General climatology
Because of its location in North America, Minnesota experiences temperature extremes characteristic of a continental climate, with cold winters and mild to hot summers in the south and frigid winters and generally cool summers in the north. Each season has distinctive upper air patterns which bring different weather conditions with them. The state is nearly from any large body of water, and temperatures and precipitation vary widely. It is far enough north to experience temperatures and blizzards during the winter months, but far enough south to have temperatures and tornado outbreaks in the summer. The variation between Minnesota's highest and lowest temperature is the eleventh largest variation of any U.S. state, and 3rd largest of any state east of the Rocky Mountains behind North Dakota and South Dakota.Minnesota is far from major sources of moisture and is in the transition zone between the moist East and the semi-arid Great Plains. Annual average precipitation across the state ranges from around in the southeast to in the northwest. Snow is the main form of precipitation from November through March, while rain is the most common the rest of the year. Annual snowfall extremes have ranged from over in the rugged Superior Highlands of the North Shore to as little as in southern Minnesota. It has snowed in Minnesota during every month with the exception of July, and the state averages 110 days per year with snow cover of an inch or greater.
Lake Superior
Lake Superior moderates the climate of those parts of Minnesota's Arrowhead Region near the shore. The lake acts as a heat sink, keeping the state's North Shore area relatively cooler in the summer and warmer in the winter. While this effect is marked near the lake, it does not reach very far inland. For example, Grand Marais on the lakeshore has an average July high temperature of, while Virginia, at about the same latitude but inland about to the west, has an average July high of. Virginia's average high temperature in January is, while Grand Marais’ is. Just a few miles inland from Lake Superior are the Sawtooth Mountains, which almost completely confine the marine air masses and associated precipitation to lower elevations near the lake.The prevailing northwest winter winds also limit the lake's influence. Places near the shoreline can receive lake-effect snow, but because the state lies north and west of the lake, snowfall amounts are not nearly as large as they are in locations like Wisconsin and Michigan that lie downwind to the south. Even so, the single largest snowstorm in Minnesota history was a lake effect event. On January 6, 1994, Finland, Minnesota, received of lake effect snow in 24 hours, and over a three-day period. Both are Minnesota records. At per year, the port city of Duluth has the highest average snowfall total of any city in Minnesota. At, Grand Marais has the lowest average summer temperature of any city in the state.
The climatological effects of Lake Superior tend to stifle convection, thus limiting the potential for tornadoes. Although Cook and Lake counties are two of the largest counties in the state, they have experienced only seven tornadoes in the past 56 years. One of those tornadoes was a large F3 that occurred in the Tornado outbreak of August 6, 1969.
Climate
Temperature
Precipitation
Full statistics for selected cities 1981–2010
Seasons
Winter
Even though winter does not officially start until late December, Minnesota usually begins experiencing winter-like conditions in November, sometimes in October. As with many other Midwestern states, winter in Minnesota is characterized by cold temperatures and snowfall. Weather systems can move in from the north, west, or south, with the majority of the weather being driven in from the north. A vigorous jet stream brings high and low-pressure systems through in quick succession, which can cause large temperature variations over a short period of time.Winter temperature
As the last remnants of summertime air in the southern U.S. start to lose their grip, cold polar air building up in northern Canada starts to push farther south, eventually spreading into Minnesota. By the time December and January arrive, Minnesota is fully engulfed in the polar air and is then subjected to outbreaks of arctic air masses. Because there are no natural barriers north or northwest of Minnesota to block arctic air from pouring south, Minnesota gets regular shots of the arctic air through the winter. High pressure systems which descend south from the Canadian plains behind the fronts bring light winds, clear skies, and bitterly cold temperatures. The northern part of Minnesota gets the brunt of the cold air. International Falls, sometimes called the "Icebox of the nation", has the coldest average annual temperature of any National Weather Service first-order station in the contiguous United States at. Tower, Minnesota, sinks below on an average of seventy-one days per year, while the ten coldest counties in the contiguous US, based on January minimums, are all located in Minnesota. The air mass then slowly moderates as it moves south into the rest of the state. Alberta clippers alternate with these high-pressure systems, bringing high winds and some snowfall with them.Image:Winter in St. Paul.jpg|thumb|left|A wintry February day in St. PaulMinnesota occasionally gets breaks from the polar and arctic air when a zonal flow takes hold. This means that the jet stream will move in a west to east motion—rather than north to south—and warmer air from the western United States is pushed into the region. In Minnesota this pattern commonly leads to a prolonged period of above freezing high temperatures that gives Minnesotans a break from the winter freeze. Storms that move into Minnesota from a more westerly direction generally do not bring significant amounts of precipitation with them. This pattern becomes especially common when El Niño is present, as the jet stream is weakened and pushed further north into Canada, therefore arctic air is often blocked from entering Minnesota. The opposite phase, La Niña, amplifies the jet stream, therefore arctic air intrusions become even colder and more prevalent.