Frost hits most areas

A daytime frost has ended the growing season for most area plants, data from WeatherUnderground indicates. Depending on your location, the growing season length in 2011 was between 233 and 235 days. The average growing season in Chicago is expected to be between 170 and 175 days, according to the State Meteorologist.

However, pockets of warmer temperatures, buildings and other shelter could lengthen the growing season still, as not all stations have reported frost.

In the Ravenswood neighborhood, the frost can be measured through five weather stations that post logs of weather.

  • Irving Park Kilchica69 reported the temperatures hit 32° F at 2A and didn’t rise above freezing till 10.54A, with winds below gusting as high as 13 mph, but generally under 5 mph, the frost here was nearly 9 hours long. The thermometer went back down to 32° F at 9.15P, staying cool until 1.32A this morning.
  • Lincoln Square Kilchica105 reports temperatures hit freezing at 2.41A yesterday and remained in the freeze range till 8.32A yesterday. The station did not report a frost last night.
  • North Park Kilchica58 reports temperatures rose above freezing at 12.30A, a three hour frost that started at 9.30P Thursday, after a first frost lasting from 2.30A to 10.30A Thursday.
  • Kirzanadu, located in Lakeview, Kilchica63, reports no frost yet. If you live by the lake, the growing season continues!
  • Just a few blocks away, however, Wrigleyville Kilchica60, reports frost hit at 2.46A Thursday and didn’t lift till 10.46A. Weather is very localized.

With the first frost out of the way (except for Lakeview), we can consider the first measurable snowfall. (Did you notice the freezing rain earlier in the month? It was rated as our first snowfall of the season, according to weather guru Tom Skilling.)

According to the National Weather Service the earliest snowfall in a season hit Chicago on September 25, 1928 with the earliest measurable snowfall happening on October 12, 1909.

When do you think the first measureable snow fall will happen in the hood? Last year it happened on December 1.


Tom Skilling talks about frost.

Tom Skilling on the first snowfall of 2011.

Learn more: Illinois state climatologist Jim Angel, PhD defines a frost.

Learn more: Illinois state climatologist Jim Angel, PhD discusses the growing season.

Learn more: Illinois State Water Survey updated frost dates.

Learn more: Great Chicago Snow storms.

Learn more: Chicago snowfall statistics.

No freeze here yet

It may have been kissed by Mr. Frost but not enough for a a freeze. 2400 block of W Cullom 11/11/11 7:30 am Photo credit: Jane Rickard

It was cold Friday morning. Colder than it has been in this area since March.

But it wasn’t a freeze. Not yet.

According to WeatherUnderground, the Irving Park station KILCHICA69 recorded a temperature low of 33.1° F for about 20 minutes starting at 6.30A Friday. The new KILCHICA105 station in Lincoln Square recorded an even lower reading of 32.7° F for five minutes at 6.11A.

While the West Rogers Park station KILCHICA51 hit 32° F for five minutes starting at 6.35A.

That’s on the knife edge and isn’t acceptable to define a frost. The temperature has to be BELOW freezing first. A condition that means our growing season is now at about 228 days with the next chance of a freeze being on Wednesay night.

Enjoy this unusually beautiful weather.


Neighborhood hit by frost

The growing season in Ravenswood suffered a frost last night. The Bulldog’s resident weatherman, Tom Vollman, formerly of Kansas City weather fame, slipped through our clutches when we tried to pin him down about the temperatures that may have led to a frost during Friday morning’s rush hour. But there should be no doubt that early this morning the temperature and other characteristics of a frost were in the neighborhood.

We suffered a frost. (Vollman said if there was any doubt about the Friday event, there wouldn’t be about the Saturday frost. So I guess he has us there.)

According to the Weather Underground station located in Irving Park, about two miles west of most of the neighborhood, the temperature dipped below the freezing point for pure water, 32° F, at 2:08A this morning. Temperatures are rising back to 32° F this hour, 8:42A. Also, the wind was calm, with gusts below 10 miles per hour and the wind holding at no more than 6 mph, with many readings of 0 mph. That leaves us with 6:34 hours of below freezing temperatures.

The term freeze and frost, while similar, describe different weather conditions. With sustained low temperatures and light winds, this is most likely a frost. A freeze happens when the temperatures dip lower and the winds generally increase. A frost does not occur every year because sometimes a killing frost will happen first.

A Weather Underground station in Rogers Park, just north of the Rosehill Cemetery, also reports frost-like conditions, with calm winds and temperatures dropping below 32° F at 2:44A and remaining there till 8:33A this morning, a period of 5:49 hours.

The final local Weather Underground station in Uptown reports temperatures broke 32° F at 6:44A and remain at 31° F at the time of the most recent reading, 8:47A. That indicates a frost period of at least 2:03 hours. That station is located just east of Graceland Cemetery.

The current temperature at WGN TV studios is 32.9° F, indicating the frost has passed in that area.

Frost conditions are very localized. A frost happens when the winds are calm and the sky is clear. Both these conditions happened early this morning. In addition, the temperatures hold to just below freezing. Under these conditions colder air settles near the ground and warmer air rises.

The temperature may vary from ground-level freeze to a warmer temperature just two meters above the ground. A frost such as we had last night is likely to end the growing season of most small plants and containers. If you protected your plants last night they may continue to grow. Larger and hardier plants and plants that still have tree leaves protecting them may also have survived.

With the end of the frost, we enter a period of waiting for additional weather conditions: the killing freeze, a heavy frost and the first snowfall of the season. The first snowfall can take two forms, precipitation that does not cover the ground and ground cover.

National Weather Service, which maintains records of these events since 1885, says only two Novembers have had no snowfall, most recently in 2001, but also in 1999. Several have only reported trace snowfalls.

Here is what we wrote previously about this:

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.

Was it a frost? Temps dip to 32F this morning

The Bulldog has been watching the weather, waiting for the end of the growing season.

A light frost may have occurred in parts of the Ravenswood neighborhood during the morning rush. Three weather stations report temperatures dipped below 33 F for a period of about an hour.

In addition, the winds were calm with bright sunny skies. Was it a light frost?

The readings:

A Weather Underground station located about two miles west of the neighborhood in Irving Park says the temperature dipped below 33 F for 1 hour, 7 minutes at 7:22A today.

A different Weather Underground station located in Uptown, about a half mile east and that much closer to the lake says the temperature hit 34 F, but didn’t dip below that, for a period of an hour, starting at 7:38A.

Finally a third Weather Underground station located north of the community, near Rosehill Cemetery says the temperature dipped below 33 F for just 18 minutes, starting at 7:57A.

None of the temperature reported to have dropped below 32 F. Conditions can be highly localized.

Do you see signs of a frost?