December 15: ORD

Today is December 15th. It's the 349th day of the year. 16 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 34 and the normal low is 20. I've calculated the 32-year averages at 38 and 22.

On the warm side, in 1998 the high was 51 with a low of 37. In 1992 the high was 56 with a low of 31. A year later, in 1993, the high was 46 with a low of 38. In 1984 the high was 50 with a low of 33. In 1990 the high was 45 with a low of 34. Other warm highs were 47 in 1986, 46 in 1996 and 46 in 1997. Other warm lows were 33 in both 1982 and 1999. The record high of 64 was set in 1971. The record warmest low of 44 was set back in 1928. Over the last 32 years, 23 highs (72%) were in the: 30s (13) and 40s (10). Three highs were in the warmer 50s. Six highs were in the cold: 10s (aka teens)(1) and 20s (5).

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 39 with a low of 32, a seven degree spread. In 1974 the high was 43 with a warm low of 36, a seven degree spread. In 1973 the high was 28 with a low of 26, a mere two degree spread. In 1971 the high was 62 with a low of 39, a warm day and year of the record high. In 1964 the high was 30 with a cold low of 1, a cold day. In 1963 the high was 11 with a low of -6, a cold day. In 1959 the high was 52 with a low of 34, a warm day. In 1958 the high was 14 with a low of -9, a cold day.

More recently, there were no large spreads of 30 degrees or more. There were small spreads of five degrees in 1982 (38/33), five degrees in 1999 (38/33) and six degrees three years ago (31/25).

On the cold side, in 1989 the high was 16 with a low of -8. In 2000 the high was 31 with a low of 3. In 1988 the high was 27 with a low of 7. In 1981 the high was 22 with a low of 12. Other cold lows were 5 two years ago, 7 in 1991 and 8 last year. The record low of -12 and record coldest high of -2 were set on the same day way back in 1901. 21 of the last 32 lows (66%) were: 20s (11) and 30s (10). 11 lows (34%) were in the cold: negative 0s (1), 0s (aka single digits)(5) and 10s (aka teens)(5). Yesterday was the 3rd coldest December 14 of the last 33 years as was the previous day, December 13. This represents the coldest 9% of each date.

In 1973, O'Hare had 3.2 inches of snow today. This was the third day of a string of days through the 20th which produced 17.6 inches, or 94% of the month's total of 18.8 inches. In 1987, O'Hare had 8 inches, day two of a two-day storm of 9.1 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:43 and sunrise is at 7:15. Sunset is at 16:22 and twilight ends at 16:54. There's a total of 9 hours, 7 minutes of daylight today and 10 hours, 11 minutes between twilights. We are losing a minute of daylight per day. Tomorrow twilight begins at 6:44 and sunrise is at 7:16. The moon reached first quarter two mornings ago at 7:59 and is waxing gibbous. Illumination was 66% at midnight, will be 70% at noon and 74% at midnight tonight. Moonset is at 1:29 this morning. Moonrise is at 12:31 this afternoon. Moonset is at 2:20 tomorrow morning. Moonlight time is 12 hours, 58 minutes which is 35 minutes longer than yesterday.

Bill of Rights Day is today. Christmas Eve is in nine days and Christmas Day is in ten days. -Bernie-