The climate of Minnesota is typical of a continental climate, with cold winters and hot summers. The state's location in the Upper Midwest allows it to experience some of the widest variety of weather in theUnited States, with each of the four seasons having its own distinct characteristics. The areas near Lake Superior in the Minnesota Arrowhead region experience weather unique from the rest of the state. The moderating effect of Lake Superior keeps the surrounding area relatively cooler in the summer and relatively warmer in the winter, giving that region more of a maritime climate. On the Köppen climate classification, the southern third of Minnesota—roughly from the Twin Cities region southward—falls in the hot summerhumid continental climate zone (Dfa), and the northern two-thirds of Minnesota falls in the warm summer humid continental climate zone (Dfb).
Winter in Minnesota is characterized by cold (below freezing) temperatures. Snow is the main form of winter precipitation, but freezing rain, ice, sleet, and occasionally rain are all possible during the winter months. Common storm systems include Alberta clippers or Panhandle hooks; some of which evolve intoblizzards. Annual snowfall extremes have ranged from over 170 inches (432 cm) in the rugged Superior Highlands of the North Shore to as little as 10 inches (25 cm) in southern Minnesota. Temperatures as low as −60 °F (−51 °C) 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 fall.
In summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north. These humid conditions help kick off thunderstorm activity 30–40 days per year. Summer high temperatures in Minnesota average in the mid-80s F (30 °C) in the south to the upper-70s F (25 °C) in the north, with temperatures as hot as 114 °F (46 °C) possible. The growing season in Minnesota varies from 90 days per year in the Iron Range to 160 days in southeast Minnesota. Tornadoes are possible in Minnesota from March through November, but the peak tornado month is June, followed by July, May, and August. The state averages 24 tornadoes per year. Minnesota is the driest state in the Midwest. Average annual precipitation across the state ranges from around 35 inches (890 mm) in the southeast to 20 inches (510 mm) 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 re-strengthen, 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. Fall and spring are the windiest times of the year in Minnesota.
Because of its location in the center of 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.[1] Each season has distinctive upper air patterns which bring different weather conditions with them. Being 1,000 miles (1,609 km) from any large body of water (with the exception of Lake Superior), Minnesota receives temperatures and precipitation that vary widely. It is far enough north to experience −60 °F (−51 °C) temperatures and blizzards during the winter months, but far enough south to experience 114 °F (46 °C) temperatures and tornado outbreaks in the summer.[2] The 174 degree Fahrenheit (97 °C) variation between Minnesota's highest and lowest temperature is the 11th largest variation of any U.S. state, and 3rd largest of any non-mountainous state (behind North Dakota and South Dakota).[3]
Minnesota is far from major sources of moisture and is in the transition zone between the moistEast and the arid Great Plains. Annual average precipitation across the state ranges from around 35 inches (890 mm) in the southeast to 20 inches (510 mm) in the northwest.[4] 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 170 inches (432 cm) in the rugged Superior Highlands of the North Shore to as little as 2.3 inches (5.8 cm) in southern Minnesota.[5][6] 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 (2.5 cm) or greater.[7]
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.[9] 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 70 °F (21 °C), while Virginia, at about the same latitude but inland about 100 miles (161 km) to the west, has an average July high of 77 °F (25 °C). Conversely, Virginia's average high temperature in January is 15 °F (−9 °C), while Grand Marais' is 23 °F (−5 °C).[10] Just a few miles inland from Lake Superior are the Sawtooth Mountains, which largely confine the marine air masses and associated precipitation to lower elevations near the lake.[11]
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.[8] Even so, the single largest snowstorm in Minnesota history was a lake effect event. On January 6, 1994 Finland, Minnesota, received 36 inches (91 cm) of lake effect snow in 24 hours, and 47 inches (119 cm) over a three day period. Both are Minnesota records. At 85 inches (216 cm) per year, the port city of Duluth has the highest average snowfall total of any city in Minnesota.[12] At 58.9 °F (14.9 °C), Grand Marais has the lowest average summer temperature of any city in the state.[13]
The climatological effects of Lake Superior tend to stifle convection, thus limiting the potential for tornadoes.[7] Although Cook and Lakecounties are two of the largest counties in the state, they have experienced only 7 tornadoes in the past 56 years.[14] One of those tornadoes was a large F3 that occurred in the 1969 Minnesota tornado outbreak.
Source : http://en.wikipedia.org/
No comments:
Post a Comment