December 18: ORD

Today is December 18th. It's the 352nd day of the year. 13 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 18.

On the warm side, in 2002 the high was 55 with a low of 37. In 1998 the high was 53 with a low of 32. A year earlier, 1997, the high was 46 with a low of 32. Four years later, in 2001, the high was 48 with a low of 29. In 1993 the high was 41 with a low of 35, a six degree spread. In 1982 the high was 43 with a low of 32. Other warm lows were 33 in 1995, 31 in 1978 and 31 last year. The record high of 62 and record warmest low of 43 were set on the same day way back in 1877. Over the last 32 years, 14 highs (44%) were in the 30s. Eight highs (25%) were in the warmer: 40s (6) and 50s (2). Ten highs (31%) were in the cooler: 0s (aka single digits)(1), 10s (aka teens)(5) and 20s (4).

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 42 with a warm low of 36, a six degree spread and warm day. In 1976 the high was a warm 47 degrees. In 1975 the high was 17 with a low of 4, a cold day. In 1973 the high was 26 with a low of 20, a six degree spread. In 1970 the high was 46 with a low of 37, a warm day. In 1968 the high was 37 with a warm low of 32, a five degree spread. In 1967 the high was 48 with a low of 33, a warm day. In 1964 the high was 18 with a low of 0, a cold day. In 1963 the high was 9 with a low of -9, a cold day. In 1962 the high was 53 with a low of 32, a warm day. In 1961 the high was 35 with a low of 29, a six degree spread.

More recently, there were no large spreads of 30 degrees or more. There were small spreads of four degrees in 1995 (37/33), five degrees in 1986 (34/29), five degrees last year (36/31) and seven degrees in 1990 (37/30).

On the cold side, in 1983 the high was 3 with the record low of -11. Two years later, in 1985, the high was 10 with a low of -9. In 2000 the high was 16 with a low of -1. In 1989 the high was 16 with a low of 2. In 2005 the high was 15 with a low of 4. In 1996 the high was 18 with a low of 7. Two years ago the high was 23 with a low of 3. In 1991 the high was 22 with a low of 7. Other cold lows were 6 in 1999 and 7 in 1981. The record coldest high of 1 was set way back in 1884. 29 of the last 32 lows (91%) were: 0s (aka single digits)(7), 10s (aka teens)(7), 20s (6) and 30s (9). Three lows were in the cold: negative 10s (1) and negative 0s (aka negative single digits)(2).

In 1973, O'Hare had 0.6 inches of snow today. This was the sixth day of a string of eight days through the 20th which produced 17.6 inches, or 94% of the month's total of 18.8 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:45 and sunrise is at 7:17. Sunset is at 16:23 and twilight ends at 16:55. There's a total of 9 hours, 6 minutes of daylight today and 10 hours, 10 minutes between twilights. We are losing a minute of daylight per day. Tomorrow twilight begins at 6:46 and sunrise is at 7:18. The moon is waxing gibbous. Illumination was 89% at midnight, will be 92% at noon and 95% at midnight tonight. Moonset is at 4:38 this morning. Moonrise is at 14:08 this afternoon. Moonset is at 5:41 tomorrow morning. Moonlight time is 14 hours, 30 minutes which is 27 minutes longer than yesterday.

Christmas Eve is in six days and Christmas Day is in seven days. -Bernie-