The neighborhood seems poised to experience the arrival of the first frost. Tonight as we cover the last of the summer vegetables shivering in the garden we can take a moment to consider a few facts about the phenomena of frost we are anticipating. There are a number of related weather terms that we should explain.
- Frost: The temperature of the air reaches 32 F there are calm winds and clear skies. Under these conditions, the ground temperature may dip below 32 F while the official temperature, measured a distance of 5′ above the ground, is often warmer. The temperature will increase the next day. Many plants can survive a light frost.
- Heavy frost: The wind conditions are similar to a frost, i.e., calm winds, clear skies and a rising temperature the next day. The temperature drop is to 25 – 28 F for several hours. Most plants cannot survive a heavy frost.
- Freeze: The wind is about 5 mph or higher with temperatures below freezing. The height of the cold air mass extends to 500′ or more. Many tender plants are killed or damaged.
- Heavy freeze: Similar to the freeze. Temperature declines to 24 F or lower. Vegetation is killed the ground is frozen.
According to the Old Farmers Almanac, Chicago experiences its first frost, on average, October 26. The Illinois Climatologist says, on average, October 14. The earliest killing frost in Chicago, according to the National Weather Service, happened on October 2, 1971.
The earliest frost happened on September 22, 1974, while (sit down for this one) the earliest snowfall in the city happened on September 25, 1928, the earliest measurable snow: October 12, 1909.
According to the data from the Illinois State Weather Service, the latest frost at the Chicago Botanical Garden over the 20 year period from 1981-2000 happened on November 6.
There are a number of weather stations in the neighborhood to measure whether a frost, a freeze or even a snowfall happens. They are St. Matthias Elementary, St. Andrew Elementary, Queen of Angels Elementary, Lane Tech and WGN Studios. If all the stations that are operating on a particular date agree, we’ll declare the event to have happened on a particular date.
It would be a pity to have all these weather stations working over time without there being a bit of fun involved. Do you have a prediction of when the first frost, first freeze, first snowfall and first measurable snowfall will happen in Ravenswood? Send your educated guess or shot in the dark in the the form of a comment and we will find a way to reward those who guess correctly.
No matter what we do winter is coming our way, we might as well have some fun with Mother Nature as she changes seasons on us. A bit of fun should make the weather inside a bit warmer for us all.
Related posts:
- 201 Miles to Springfield: Ameya Pawar coming out swinging
