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Category Archives: Seasons
Higher overnight lows led to warm September
As we enter the month of October and the traditional end of the warm season, it’s interesting to note that the average temperature last month, through Sept. 28, was 4.0 degrees above normal in Madison.
That is by far the biggest deviation among traditional warm-season months — June, July, August and September. All were warmer than average this year: June was 0.8 degrees, July just 0.5 degree and August only 1.2 degree above the respective norm. Continue reading
Are day and night of equal hours on the equinox?
This year, the autumnal equinox occurred on Saturday, Sept. 23, at 1:50 a.m. Central Time. During the equinox, the sun shines directly on the equator as its position moves from one hemisphere to the other. The word “equinox” is derived from the Latin word “aequus,” which means “equal,” and “nox,” which is the Latin word for “night.” During the 24 hours of the equinox, there are about 12 hours of day and 12 hours of night.
You may hear that daylight and nighttime are of equal length on the equinox. But during the equinox at our midlatitude location, there are approximately eight more minutes of daylight for two reasons: the sun’s shape and atmospheric refraction. Continue reading
Why are cities hotter than the surrounding rural areas?
On average, the city is warmer than the countryside. This difference in temperature is referred to as the urban heat island effect. A number of factors contribute to the relative warmth of cities, such as heat from industrial activity, the thermal properties of buildings and the evaporation of water.
For example, the heat produced by heating and cooling city buildings, and running planes, trains, buses and automobiles contributes to the warmer city temperatures. Heat generated by these objects eventually makes its way into the atmosphere, adding as much as one-third of the heat received from solar energy. Continue reading
Category: Climate, Meteorology, Seasons
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Winter in July?
On more than one occasion in this column we have commented on the areal extent of air colder than 23 degrees about 1 mile above the ground as a measure of the extremity of winter.
In the middle of January, about 68 million square kilometers of the Northern Hemisphere are covered by air that cold at that level. Between about July 5 and July 20 that area shrinks to zero, and the complete absence of such air lasts only a very few days. Continue reading
Were May and June unusually dry in Madison?
While we all contended with the remarkable and dangerous smoke in the sky this past week, we also wrapped up a record dry spell in Madison’s history.
The 61 days of May and June 2023 were the driest May and June ever, with a paltry 2.01 inches of total precipitation falling. The next closest rival on this ignominious list occurred in May and June 1992, when only 2.65 inches of rain fell during the two months. Individually, May and June were the sixth-driest May and June in Madison’s history, suggesting how rare it is for both of them to be so void of precipitation. Continue reading
Category: Climate, History, Meteorology, Seasons
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