Wednesday, December 23, 2009

December 23: ORD

Today is December 23rd. It's the 357th day of the year. Eight days remain. It's week 51 of the year.

Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980.


According to the National Climatic Data Center (NCDC), the normal high is 32 and the normal low is 18. I've calculated the 31-year averages at 34 and 19.


On the warm side, in 1979 the high was 62 with a low of 46. That high of 62 ties the record, but O'Hare was not the official station of record in 1979. In 1982 the high was the record high of 62 with a low of 42. In 1996 the high was 52 with a low of 32. In 1988 the high was 48 with a low of 33. In 2005 the high was 44 with a low of 37, a seven degree spread. In 1994 the high was 42 with a low of 35, a seven degree spread. In 2006 the high was 40 with a low of 33, a seven degree spread. Another warm high was 52 in 2007, just two years ago. Of course, the low that day was a cold 14 degrees, evidence of a cold front. Other warm lows were 32 in 1997, 31 in 1980 and 30 in 1987. The record warmest low of 49 occurred way back in 1877.
Over the last 31 years, 19 highs were in the: 30s (12) and 40s (7). Four highs were in the warmer: 50s (2) and 60s (2). Eight highs were in the cooler: negative single digits (1), 0s (aka single digits) (1), 10s (aka teens) (3) and 20s (3).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1976 the low was a cold 6 degrees. In 1975 the high was 34 with a low of 27, a seven degree spread. In 1972 the high was 32 with a low of 30, a mere two degree spread. In 1971 the high was 46 with a low of 33, a warm day. In 1969 the high was 28 with a low of 24, a four degree spread. In 1965 the high was 55 with a low of 41, a warm day. In 1964 the high was 48 with a low of 37, a warm day. In 1963 the high was 22 with a low of -8, a 30 degree spread and cold day. In 1962 the high was 24 with a low of 0, a cold day. In 1961 the high was 31 with a low of 24, a seven degree spread. In
1960 the high was 11 with a low of -17, a very cold day. In 1959 the high was 29 with a low of 25, a four degree spread.

More recently, there w
as a large spread of 38 degrees in 2007 (52/14). There were small spreads of five degrees in 1986 (34/29), five degrees in 1997 (37/32), seven degrees in 1980 (38/31) and seven degrees in 1995 (30/23).

On the cold side, in 1983 the high was the record coldest high of -6 with the record low of -21. In 1989 the high was 8 with a low of -11. A year later, in 1990, the high was 11 with a low of 0. A decade later, in 2000, the high was 20 with a low of -4. A year earlier, in 1999, the high was 16 with a low of 3. In 2004 the high was 18 with a low of 5. 16 of the last 31 lows were: 20s (8) and 30s (8). 13 lows were in the cooler: negative 20s (1), negative 10s (1), negative single digits (1), single digits (6) and 10s (aka teens) (4). Two lows were in the warmer 40s.

In 1969, O'Hare had 9.9 inches of snow today. This was the third of four days of a total of 13.5 inches of snow. In 1961 Midway had 10.2 inches of snow. O'Hare had 7.4 inches in 1961, part of a 3-day event of 8.2 inches (including half an inch on the 21st and three tenths on the 22nd).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:48 and sunrise is at 7:20. Sunset is at 16:25 and twilight ends at 16:57. Chicago's sunset is at 16:24 and twilight ends at 16:56. Tomorrow twilight begins at 6:48 and sunrise is at 7:20. There's a total of 9 hours, 5 minutes of daylight today and 10 hours, 9 minutes between twilights. The moon is waxing crescent and will reach first quarter tomorrow at 11:36. Illumination was 36% at midnight, will be 41% at noon and 45% at midnight tonight. Moonrise is at 11:01. Moonset is at 23:34 late tonight. Moonlight time is 12 hours, 33 minutes which is 40 minutes longer than yesterday. The Winter Solstice was two days ago at 11:47.

Christmas Eve is tomorrow and Christmas Day is in two days. New Year's Eve is in eight days and New Year's Day is in nine days. -Bernie-

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