Recent Articles
  • Saturday heat/humidity gave way to cooler less humid air

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  • Air temperature in the sun and in the shade

    Dear Tom, Parade Magazine’s Marilyn Savant says air temperature is the same in the sun as in the shade, but placing a thermometer in the sun heats up the thermometer. Does that make sense? If true, what do they use to measure air temperature? Mike Beirl, Bolingbrook Dear Mike, Air temperature is always measured in a shady location because in the shade the thermometer is measuring the actual air temperature, and only the air temperature. A thermometer placed in the […]

  • Why you will never hear of a wind speed of 11 mph in a weather report

    Dear Tom, I have never heard a wind speed of 11 mph in a weather report, and I have listened for years. Bill Walkor, Chicago Dear Bill, You are correct to observe that a wind speed of 11 mph has never been announced. This may seem strange, but here’s the explanation. The National Weather Service measures wind speeds in knots (nautical miles per hour) in accordance with international practice. However, in the United States we use statute miles for measures […]

  • On the solstices at Chicago, how many degrees north or south of due east and due west are the sunrises and sunsets?

    Dear Tom, On the solstices at Chicago, how many degrees north or south of due east and due west are the sunrises and sunsets? Frank Stachyra, Oak Park Dear Frank, Chicago experiences a sunrise directly in the east twice a year on the spring and fall equinoxes. On those days, the sun also sets directly in the west and if the weather is clear, east-west travel is difficult as the sun’s rays shining directly down the streets make it difficult […]

  • Where and how often do derechos occur?

    Dear Tom, I’m wondering where and how often derechos occur. Margaret Robertson Chicago Dear Margaret, Severe thunderstorms can occur anywhere, given the ingredientsof warmth, moisture, instability, converging low-level winds and diverging winds aloft. The Midwestis prone to derechos, a high wind event in which winds,often in excess of 100 mph, plow out of a line of fast-moving thunderstorms, producing swaths of damage that extend for hundreds or even thousands of miles.The highest incidence is from midsummer through early fall. Chicago […]

  • Brief warming/Storms possible Thursday – workweek ends on windy note

    With deep low pressure passing to our west and north Thursday, first the associated warm front will move through the Chicago area from the south late in the day, followed soon aft     er by the storm’s cold front. This puts a least a portion of our area in the position of briefly experiencing the “warm sector” of this storm system- strong late afternoon-early evening warming well into the 60s and t-storms (a few severe storms possible). Strong westerly winds gusting […]

  • What are the world high and low temperature records, and Chicago’s?

    Dear Tom, What are the world high and low temperature records, and Chicago’s? Alvira Franko, Chicago Dear Alvira, Of all the world’s locations that are candidates for extreme temperature occurrences, two places rank above all others: Deserts for heat and polar regions for cold. Among the world’s deserts, Death Valley, California, claims the world’s heat record: 134 degrees recorded there on July 10, 1913. Death Valley is located in the east-central part of the Mojave Desert. The Earth’s south polar […]

  • Did Chicago’s 2018 precipitation set a new record?

    Dear Tom, 2018 sure seemed like a wet year in Chicago history. Did we break the city’s annual precipitation record? Thanks, Doug Congdon Zion Dear Doug, We did not, but we came close. According to Chicago weather historian Frank Wachowski, 2018 with 49.23 inches of precipitation was the city’s fourth wettest year dating back to 1871, surpassed only by 2008-50.86 inches, 2011-49.83 inches and 1983-49.35 inches. May was the wettest month of the year logging 8.21 inches, followed by 7.63 […]

  • Barbaric cold vaporizes hot water

    Science experiment in Kenosha, Wisconsin– Near-boiling water evaporates before it hits the ground!

  • Based on past history, what date of the year is it most likely to snow in Chicagoland?

    Dear Tom, Based on past history, what date of the year is it most likely to snow in Chicagoland? — Leslie Rosenwinkel, Glen Ellyn Dear Leslie, Based on data dating to the winter of 1884-85, Chicago’s historical season for measurable snowfall (at least 0.1 inche) extends from Oct. 12 through May 11. We asked Chicago climatologist Frank Wachowski to crunch the numbers, and he reported that the city’s dates with the most frequent measurable snowfalls over that period were Jan. […]

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