December 20: ORD

Today is December 20th. It's the 354th day of the year. 11 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 32 and 17.

On the warm side, in 1988 the high was 56 with a low of 32. This is one of only two highs in the 50s in the history of O'Hare (see 1967 below). Two years later, in 1990, the high was 49 with a low of 30. Four years after that, in 1994, the high was 42 with a low of 34 (our most recent 30s low). The record high of 67 and record warmest low of 55 were set on the same day way back in 1877. Back then, official readings for the area were taken adjacent to Lake Michigan. Over the last 32 years, 14 highs (44%) were in the 30s. Eight highs (25%) were in the warmer: 40s (7) and 50s (1). Ten highs (31%) were in the cold: 0s (aka single digits)(1), 10s (aka teens)(4) and 20s (5). The most recent 10s high was 17 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. In 1972 the high was 37 with a warm low of 34, a mere three degree spread. In 1968 the high was 33 with a low of 26, a seven degree spread. In 1967 the high was 55 with a low of 36, a warm day. In 1966 the high was 36 with a low of 32, a four degree spread. In 1965 the high was 35 with a low of 29, a six degree spread. In 1964 the low was a cold 7 degrees. In 1963 the high was 6 with a low of -16, a cold day. That low of -16 was colder than the record low of -9, set at Midway. The high of 6 was near the record coldest high of 4, set way back in 1901. In 1960 the high was 22 with a cold low of 6, a cold day. In 1959 the high was 31 with a low of 28, a mere three degree spread. In 1958 the high was a cold 21 with a low of 8, a cold day.

More recently, there was a large spread of 32 degrees in 1999 (37/5). There were small spreads of five degrees in 1991 (35/30) and six degrees in 2002 (35/29).

On the cold side, in 1989 the high was 5 with a low of -6. In 1980 the high was 10 with a low of -1. In 2000 the high was 17 with a low of -5, our most recent negative single digit low. In 1983 the high was 20 with a low of -1. In 1996 the high was 17 with a low of 3. In 1981 the high was 22 with a low of -1. In 1985 the high was 19 with a low of 3. In 2005 the high was 21 with a low of 5. Another cold low was 5 in 1999. The record low of -9 was set in 1963. The record coldest high of 4 occurred way back in 1901. 14 of the last 32 lows (44%) were 20s. 14 lows (44%) were in the cold: negative single digits (5), single digits (4) and 10s (aka teens) (5). Four lows (12%) were in the warmer 30s.

In 1973, O'Hare had 0.1 inches of snow today. This was the eighth day of a string of eight days which produced 17.6 inches, or 94% of the month's total of 18.8 inches. In 1960, Midway had 11 inches while O'Hare had just 3.1 inches. O'Hare also had 1.1 on the 19th.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:46 and sunrise is at 7:18. Sunset is at 16:24 and twilight ends at 16:56. There's a total of 9 hours, 6 minutes of daylight today and 10 hours, 10 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 is waxing gibbous, heading towards the full Cold or Long Nights moon tomorrow morning at 2:13. Illumination was 99% at midnight, will be 100% at noon and 100% at midnight tonight. Moonset is at 6:41 this morning. Moonrise is at 15:52 this afternoon. Moonset is at 7:36 tomorrow morning. Moonlight time is 14 hours, 49 minutes which is four minutes longer than yesterday and is at it's peak. The Winter Solstice is tomorrow at 17:38.

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