December 11: ORD

Today is December 11th. It's the 345th day of the year. 20 days remain. It's week 50 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 36 and the normal low is 22. I've calculated the 32-year averages at 36 and 21.

On the warm side, in 1979 the high was 56 with a low of 34. In 1990 the high was 55 with a low of 32. In 1987 the high was 48 with a low of 34. In 2006 the high was 45 with a low of 37. Other warm highs were 49 in 1991, 49 in 1998 and 48 in 2001. Another warm low was 36 in 1996. The record high of 61 was set back in 1949. The record warmest low of 50 occurred in 1965. Over the last 32 years, 14 highs (44%) were 30s. Ten highs (31%) were in the warmer: 40s (8) and 50s (2). Eight highs (25%) were in the cold: 0s (1), 10s (1) and 20s (6).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1977 the high was 23 with a low of -7, a 30 degree spread and cold day. That low of -7 was colder than the record low. In 1976 the high was 24 with a low of 5, a cold day. In 1975 the high was 38 with a warm low of 35, a mere three degree spread. In 1972 the high was 21 with a low of -13, a 34 degree spread and cold day. That low of -13 was colder than the record low of -5, set on this day. In 1970 the high was 40 with a warm low of 35, a five degree spread. In 1968, the high was a warm 51 degrees. In 1967 the high was 40 with a warm low of 37, a three degree spread. In 1965 the high was 56 with a low of 51, a five degree spread and warm day. That low of 51 was warmer than the record warmest low of 50, set on this day. In 1964 the high was 40 with a low of 33, a seven degree spread. In 1963 the high was 30 with a low of 25, a five degree spread. In 1962 the high was 7 with a low of -4, a cold day. That low of -4 is near the record low of -5, set in 1972. 1962 is also the year of the record coldest high of 6. In 1959 the high was 43 with a warm low of 37, a six degree spread. In 1958 the high was 21 with a low of 7, a cold day.

More recently, there were no large spreads of 30 degrees or more. There were small spreads of three degrees in 1996 (39/36), three degrees in 1997 (35/32), five degrees in 1983 (38/33), five degrees in 2004 (37/32) and six degrees in 2007 (33/27).

On the cold side, in 1995 the high was 8 with a low of 1, a seven degree spread. In 1988 the high was 18 with a low of 3. Last year the high was 23 with a low of 7. In 1982 the high was 26 with a low of 9. In 1980 the high was 24 with a low of 11. Another cold low was 7 in 2005. Another cold high was 24 in 1994. The record low of -5 was set in 1972. The record coldest high of 6 occurred in 1962. 27 of the last 32 lows (84%) were: 10s (a.k.a. teens)(10), 20s (7) and 30s (10). Five lows were in the cold 0s (aka single digits). Over the last four years, we've seen an example of each category of low temperatures: 37 in 2006, 27 in 2007, 17 in 2008 and 7 last year. Each year was 10 degrees colder than the previous and in all years, the temperature had a suffix of 7.

Three recent days (December 5, 6 and 8) have each been the third coldest of the past 33 years. In other words, they were in the top 9% of cold days for each date. December 7 and 9 were the fourth coldest of their dates, in the top 12% of cold days for each.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 6:40 and sunrise was at 7:12. Sunset is at 16:21 and twilight ends at 16:53. There's a total of 9 hours, 9 minutes of daylight today and 10 hours, 13 minutes between twilights. We are losing a minute of daylight per day. Tomorrow twilight begins at 6:41 and sunrise is at 7:13. The moon is waxing crescent. Illumination was 29% at midnight, will be 33% at noon and 38% at midnight tonight. Moonrise is at 11:00 this morning. Moonset is at 22:30 tonight. Moonrise is at 11:22 tomorrow morning. Moonlight time is 11 hours, 30 minutes which is 35 minutes longer than yesterday.

Bill of Rights Day is in four days. Christmas Eve is in 13 days. -Bernie-