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As a result, the official record-lowest temperature for the state was −36 °F (−37.8 °C) recorded at Congerville on 5 January 1999. [11] In 2019, the January North American Cold Wave struck Illinois. This resulted in a new record low temperature, −38 °F (−38.9 °C), recorded on January 31, 2019, at Mount Carroll.
Warm fronts are at the leading edge of a homogeneous advancing warm air mass, which is located on the equatorward edge of the gradient in isotherms, and lie within broader troughs of low pressure than cold fronts. A warm front moves more slowly than the cold front which usually follows because cold air is denser and harder to lift from the ...
Cold, warm and occluded fronts often meet at the point of occlusion or triple point. [28] A guide to the symbols for weather fronts that may be found on a weather map: 1. cold front 2. warm front 3. stationary front 4. occluded front 5. surface trough 6. squall line 7. dry line 8. tropical wave 9. Trowal
Such maps have been in use since the mid-19th century and are used for research and weather forecasting purposes. Maps using isotherms show temperature gradients, [2] which can help locate weather fronts. Isotach maps, analyzing lines of equal wind speed, [3] on a constant pressure surface of 300 or 250 hPa show where the jet stream is located.
Despite the abnormally cold winter over sections of North America and much of Russia, most of the globe saw either average or above-average temperatures during the first four months of 2014. [118] In fact, during the cold wave, North America saw much colder temperatures than Sochi, Russia which during the time was hosting the 2014 Winter Olympics.
A bulge in the dry line may also have been forming slightly south of the low, and southerly to southeasterly surface winds were backing and increasing with time throughout the warm sector. The Tri-State supercell formed in a highly favorable area just ahead of the triple point where the cold front, warm front, and dry line met.
A statement accompanying the forecast adds, “After a weird and warm winter season last year, this winter should make cold weather fans rejoice — especially those in the Great Lakes, Midwest ...
Official monthly mean temperatures have ranged from 10.1 °F (−12.2 °C) in January 1977 to 81.3 °F (27.4 °C) in July 1955, both recorded at Midway, [16] while the annual mean temperature has ranged from 45.1 °F (7.3 °C) in 1875, as recorded at the Roanoke Building, to 54.5 °F (12.5 °C), as recorded at O'Hare. [16]