Recent Articles
  • What are Chicago’s November snowfall statistics?

    Dear Tom, What are Chicago’s November snowfall statistics? James Bettelford Dear James, Chicago’s snowfall records began in 1884 and in the 135 years (through 2018) since then, two Novembers recorded no snow at all. Only traces of snow (less than 0.1 inch) were recorded in 28 of those years; the remaining 105 Novembers registered at least 0.1 inch of snow. Nov. of 1940 recorded the greatest amount of snow: 14.8 inches. Nov. of 1895 came in second, with 14.5 inches. […]

  • Warmer than normal temps on tap here the next 2 weeks; the northbound moisture with Tropical Storm“Imelda’s” remnants, responsible for up to 21” of rain & twisters in the Houston, TX area Wed, may fuel Sunday downpours here


  • What are heating and cooling degree days?

    Dear Tom, What are heating and cooling degree days? Colin McIntyre,  Chicago Dear Colin, Heating and cooling degree days are measures that indicate the departure of a day’s average temperature from a base of 65 degrees. When the day’s average temp (the sum of the midnight-to-midnight, CST, high and low temperatures, divided by two) is below 65 degrees, the number of degrees of departure is called heating degree days; when above, cooling degree days. Degree day units are a useful […]

  • Dry conditions following cool, wet first half of summer

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  • 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 […]

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