The Continental Divide dips down to 11,990 feet (3,655 m) at Loveland Pass.The climate of Colorado is quite complex compared to most of the United States. Unlike in other states, the southern Colorado is not necessarily warmer than the northern Colorado. Mountains and surrounding valleys greatly affect local climate. As a general rule, with an increase in elevation comes a decrease in temperature and an increase in precipitation. A main climatic division in Colorado occurs between the Rocky Mountains on the west and the plains on the east with the foothills forming a transitional zone between the two.
Eastern Plains
The climate of the Eastern Plains is a continental climate (Koppen climate classification BSk) of low humidity and moderate precipitation, usually from 15 to 25 inches (380 to 630 mm) annually. The area is known for its abundant sunshine and cool clear nights, which give this area the highest average diurnal temperature range in the United States[citation needed]. In summer, this area can have many days above 95 °F (35 °C) and sometimes 100 °F (38 °C), although 105 °F (41 °C) is the maximum in the front range cities above 5,000 ft (1,500 m). In the plains, the winter extremes can be from 0 °F (−18 °C) to −10 °F (−23.3 °C) and −15 °F (−26.1 °C). The all time low in the area was −40 °F (−40.0 °C) About 75% of the precipitation falls within the growing season, from April to September, but this area is very prone to droughts. Most of the precipitation comes from thunderstorms, which are often severe, and from major snowstorms that occur most often in the early spring, late autumn, and sometimes winter. Otherwise, winters tend to be mostly dry and cold. In much of the region, March and April are the snowiest months. April and May are normally the rainiest months, while April is the wettest month overall. The Front Range cities closer to the mountains tend to be warmer in the winter due to chinook winds which warm the area, sometimes bringing temperatures of 40 °F (4 °C) or higher in the winter. The average July temperature is 55 °F (13 °C) in the morning and 80 °F (27 °C) in the afternoon. The average January temperature is 10 °F (−12 °C) in the morning and 30 °F (−1 °C) in the afternoon, although variation between consecutive days can be 40 °F (4 °C).
West of the plains and foothills
West of the plains and foothills, the weather of Colorado is much less uniform. Even places a few miles apart can experience entirely different weather depending on the topography of the area. Most valleys have a semi-arid climate, which becomes an alpine climate at higher elevations. Humid microclimates also exist in some areas. Generally, the wettest season in western Colorado is winter while June is the driest month. This is the opposite of precipitation patterns in the east. The mountains have cool summers with many days of high temperatures around 60 °F (16 °C) to 70 °F (21 °C), although frequent thunderstorms can cause sudden drops in temperature. Summer nights are cool or even cold at the highest elevations, which sometimes get snow even in the middle of the summer. The winters bring abundant, powdery snowfall to the mountains with abundant sunshine in between major storms. The western slope has high summer temperatures similar to those found on the plains, while the winters tend to be slightly cooler due to the lack of warming winds common to the plains and Front Range. Other areas in the west have their own unique climate. The San Luis Valley is generally dry with little rain or snow, although the snow that falls tends to stay on the ground all winter.
Extreme weather
Snow highlights the rugged mountains as well as the urban and agricultural landscapes of the Colorado plains. Extreme weather is a common occurrence in Colorado. Thunderstorms are common east of the Continental divide in the spring and summer, and Colorado is one of the leading states in deaths due to lightning. Hail is a common sight in the mountains east of the divide and in the northwest part of the state. The Eastern Plains have some of the biggest hail storms in North America. Also the Eastern Plains are part of Tornado Alley and produce some of the deadliest U.S. tornadoes. Some damaging tornadoes in the Eastern Plains include the 1990 Limon F3 tornado and the 2008 Windsor EF3 tornado, which devastated the town. The plains are also susceptible to floods, which are caused both by thunderstorms and by the rapid melting of snow in the mountains during warm weather. Denver's 1901 record for number of consecutive days above 90 °F (32 °C) was broken in the summer of 2008. The new record of twenty-four (24) consecutive days surpassed the previous record by almost a week. Colorado is a relatively dry state averaging only 17 inches (430 mm) of rain per year and rarely experiences a time when some portion of the state is not in some degree of drought. The lack of precipitation contributes to the severity of wildfires in the state such as the Hayman Fire, one of the largest wildfires in US history.
Records
The highest temperature ever recorded in Colorado was 118 °F (48 °C) on July 11, 1888, at Bennett, while the lowest was −61 °F (−51.7 °C) on February 1, 1985, at Maybell.
Eastern Plains
The climate of the Eastern Plains is a continental climate (Koppen climate classification BSk) of low humidity and moderate precipitation, usually from 15 to 25 inches (380 to 630 mm) annually. The area is known for its abundant sunshine and cool clear nights, which give this area the highest average diurnal temperature range in the United States[citation needed]. In summer, this area can have many days above 95 °F (35 °C) and sometimes 100 °F (38 °C), although 105 °F (41 °C) is the maximum in the front range cities above 5,000 ft (1,500 m). In the plains, the winter extremes can be from 0 °F (−18 °C) to −10 °F (−23.3 °C) and −15 °F (−26.1 °C). The all time low in the area was −40 °F (−40.0 °C) About 75% of the precipitation falls within the growing season, from April to September, but this area is very prone to droughts. Most of the precipitation comes from thunderstorms, which are often severe, and from major snowstorms that occur most often in the early spring, late autumn, and sometimes winter. Otherwise, winters tend to be mostly dry and cold. In much of the region, March and April are the snowiest months. April and May are normally the rainiest months, while April is the wettest month overall. The Front Range cities closer to the mountains tend to be warmer in the winter due to chinook winds which warm the area, sometimes bringing temperatures of 40 °F (4 °C) or higher in the winter. The average July temperature is 55 °F (13 °C) in the morning and 80 °F (27 °C) in the afternoon. The average January temperature is 10 °F (−12 °C) in the morning and 30 °F (−1 °C) in the afternoon, although variation between consecutive days can be 40 °F (4 °C).
West of the plains and foothills
West of the plains and foothills, the weather of Colorado is much less uniform. Even places a few miles apart can experience entirely different weather depending on the topography of the area. Most valleys have a semi-arid climate, which becomes an alpine climate at higher elevations. Humid microclimates also exist in some areas. Generally, the wettest season in western Colorado is winter while June is the driest month. This is the opposite of precipitation patterns in the east. The mountains have cool summers with many days of high temperatures around 60 °F (16 °C) to 70 °F (21 °C), although frequent thunderstorms can cause sudden drops in temperature. Summer nights are cool or even cold at the highest elevations, which sometimes get snow even in the middle of the summer. The winters bring abundant, powdery snowfall to the mountains with abundant sunshine in between major storms. The western slope has high summer temperatures similar to those found on the plains, while the winters tend to be slightly cooler due to the lack of warming winds common to the plains and Front Range. Other areas in the west have their own unique climate. The San Luis Valley is generally dry with little rain or snow, although the snow that falls tends to stay on the ground all winter.
Extreme weather
Snow highlights the rugged mountains as well as the urban and agricultural landscapes of the Colorado plains. Extreme weather is a common occurrence in Colorado. Thunderstorms are common east of the Continental divide in the spring and summer, and Colorado is one of the leading states in deaths due to lightning. Hail is a common sight in the mountains east of the divide and in the northwest part of the state. The Eastern Plains have some of the biggest hail storms in North America. Also the Eastern Plains are part of Tornado Alley and produce some of the deadliest U.S. tornadoes. Some damaging tornadoes in the Eastern Plains include the 1990 Limon F3 tornado and the 2008 Windsor EF3 tornado, which devastated the town. The plains are also susceptible to floods, which are caused both by thunderstorms and by the rapid melting of snow in the mountains during warm weather. Denver's 1901 record for number of consecutive days above 90 °F (32 °C) was broken in the summer of 2008. The new record of twenty-four (24) consecutive days surpassed the previous record by almost a week. Colorado is a relatively dry state averaging only 17 inches (430 mm) of rain per year and rarely experiences a time when some portion of the state is not in some degree of drought. The lack of precipitation contributes to the severity of wildfires in the state such as the Hayman Fire, one of the largest wildfires in US history.
Records
The highest temperature ever recorded in Colorado was 118 °F (48 °C) on July 11, 1888, at Bennett, while the lowest was −61 °F (−51.7 °C) on February 1, 1985, at Maybell.
