December 21: ORD

Today is December 21st. It's the 355th day of the year. 10 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 33 and the normal low is 19. I've calculated the 32-year averages at 33 and 18.

On the warm side, in 2006 the high was 50 with a low of 38. In 1984 the high was 56 with a low of 30. A decade later, in 1994, the high was 51 with a low of 30. In 1979 the high was 48 with a low of 28. Other warm highs were 47 in 2003 (our most recent 40s high) and 45 in 1990. Another warm low was 33 three years ago. The record high of 62 was set in 1967. The record warmest low of 49 occurred way back in 1918. Over the last 32 years, 14 highs (44%) were in the 30s. Eight highs (25%) were in the warmer: 40s (5) and 50s (3). Ten highs (31%) were in the cold: 0s (aka single digits)(1), 10s (aka teens)(4) and 20s (5).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1976 the high was 19 with a low of 4, a cold day. In 1973 the high was 20 with a low of 2, another cold day. In 1972 the high was 35 with a warm low of 33, a mere two degree spread. In 1967 the high was a warm 61 with a low of 19, a 42 degree spread, a warm day and also the year of the record high. Also in 1967, the temperature fell 53 degrees to a low of 8 on the 23rd. In 1965 the high was 35 with a low of 29, a six degree spread. In 1964 the high was 40 with a low of 10, a 30 degree spread. In 1963 the high was 13 with a low of -11, a cold day. In 1962 the high was 30 with a low of 24, a six degree spread. In 1960 the high was 9 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 four degrees last year (29/25), five degrees in 1993 (29/24), five degrees in 2007 (38/33), six degrees in 2002 (34/28) and seven degrees in 1983 (23/16).

On the cold side, in 1989 the high was the record coldest high of 0 with the record low of -14. Two years ago the high was 16 with a low of -6. In 2000 the high was 19 with a low of -7. In 1999 the high was 14 with a low of 1. In 1985 the high was 18 with a low of -2. In 2005 the high was 20 with a low of 3. In 1980 the high was 21 with a low of 5. 21 of the last 32 lows (66%) were: 10s (aka teens) (8) and 20s (13). Seven lows were in the cold: negative 10s (1), negative single digits (3) and single digits (3). Four lows were in the warmer 30s.

In 1969, O'Hare had 0.3 inches of snow today. This was the first of four days of a total of 13.5 inches of snow.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:47 and sunrise is at 7:19. Sunset is at 16:24 and twilight ends at 16:56. There's a total of 9 hours, 5 minutes of daylight today and 10 hours, 9 minutes between twilights. We are staying at about the same daylight per day. It is the least amount of daylight of the year, at either 9:05 or 9:06. Tomorrow twilight begins at 6:47 and sunrise is at 7:19. The moon reaches the full Cold or Long Nights moon this morning at 2:13. Illumination was 100% at midnight, will be 100% at noon and 99% at midnight tonight. Moonset is at 7:36 this morning. Moonrise is at 16:57 this afternoon. Moonset is at 8:22 tomorrow morning. Moonlight time is 14 hours, 39 minutes which is ten minutes shorter than yesterday. The Winter Solstice is today at 17:38.

Christmas Eve is in three days and Christmas Day is in four days. -Bernie-