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 32-year averages at 34 and 20.

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. Just three years later, 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 three 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, 31 last year and 30 in 1987. The record warmest low of 49 occurred way back in 1877. Over the last 32 years, 20 highs (63%) were in the: 30s (13) and 40s (7). Four highs (12%) were in the warmer: 50s (2) and 60s (2). Eight highs (25%) were in the cold: negative single digits (1), single digits (1), 10s (aka teens) (3) and 20s (3). Our most recent 20s high was 20 degrees a decade ago in 2000.

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 warm 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 cold low of -8, a 30 degree spread and cold day. In 1962 the high was 24 with a cold 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 was a large spread of 38 degrees in 2007 (52/14). There were small spreads of one degree last year (32/31), 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. Five years later, in 2004, the high was 18 with a low of 5. 27 of the last 32 lows (84%) were: single digits (6), 10s (aka teens)(4), 20s (8) and 30s (9). Three lows were in the cold: negative 20s (1), negative 10s (1) and negative single digits (1). 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. 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 6:48 and sunrise is at 7:20. The moon reached the full Cold or Long Nights moon two mornings ago at 2:13 and is waning gibbous. Illumination was 95% at midnight, will be 93% at noon and 89% at midnight tonight. Moonset is at 9:02 this morning. Moonrise is at 19:22 tonight. Moonset is at 9:36 tomorrow morning. Moonlight time is 13 hours, 40 minutes which is 34 minutes shorter than yesterday. The Winter Solstice was two days ago at 17:38.

Christmas Eve is tomorrow and Christmas Day is in two days. -Bernie-