December 13: ORD

Today is December 13th. It's the 347th day of the year. 18 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 35 and the normal low is 21. I've calculated the 32-year averages at 36 and 22.

On the warm side, in 1993 the high was 46 with a low of 35. In 2006 the high was 45 with a low of 33. Another warm high was 49 in 1998. Another warm low was 33 in 2002. The record high of 67 was set in 1975. The record warmest low of 46 occurred back in 1920. Over the last 32 years, 18 highs (56%) were in the 30s. Eight highs (25%) were in the warmer 40s. Six highs (19%) were in the cold: 10s (aka teens)(1) and 20s (5). The last time it hit 50 or higher was 35 years ago in 1975. That year, it was 64 at O'Hare, 57 in Rockford, 67 at Midway and 60 in Marengo.

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 warm low of 36, a mere three degree spread. In 1976 the high was 23 with a low of 2, a cold day. In 1975 the high was 64 with a low of 38, a warm day and year of the record high of 67. In 1972 the high was 22 with a low of 8, a cold day. In 1970 the high was 32 with a low of 25, a seven degree spread. In 1968 the high was a warm 49 with a low of 18, a 31 degree spread. In 1966 the high was 29 with a low of 23, a six degree spread. In 1965 the low was a warm 33 degrees. In 1964 high was 35 with a low of 28, a seven degree spread. In 1963 the high was 12 with a low of -2, a cold day. In 1962 the high was 20 with a low of 2, a cold day. In 1961 the high was 16 with a low of 1, a cold day. In 1958 the high was 12 with a low of -8, a cold day.

More recently, there were no other large spreads of 30 degrees or more. There were small spreads of four degrees in 1983 (35/31), five degrees in 1984 (37/32), five degrees in 2005 (28/23), five degrees last year (37/32), six degrees in 2002 (39/33), six degrees in 2007 (34/28) and seven degrees in 1981 (36/29).

On the cold side, in 1985 the high was 12 with a low of -3. In 2000 the high was 24 with a low of -8, a 32 degree spread. In 1989 the high was 20 with a low of 6. Three years earlier, in 1986, the high was 25 with a low of 1. The record low of -13 and record coldest high of 3 were both set on the same day in 1903. 15 of the last 32 lows (47%) were 20s. Nine lows (28%) were in the cold: negative 0s (2), 0s (aka single digits)(2) and 10s (aka teens)(5). Eight lows (25%) were in the warmer 30s.

In 1973, O'Hare had 4 inches of snow today. This was the first 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.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 6:42 and sunrise was at 7:14. Sunset is at 16:21 and twilight ends at 16:53. 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 6:43 and sunrise is at 7:14. The moon reaches first quarter this morning at 7:59. Illumination was 47% at midnight, will be 52% at noon and 56% at midnight tonight. Moonrise is at 11:44 this morning. Moonset is at 29 minutes past midnight tonight. Moonrise is at 12:06 tomorrow afternoon. Moonlight time is 12 hours, 16 minutes which is 8 minutes longer than yesterday.

Bill of Rights Day is in two days. Christmas Eve is in 11 days. -Bernie-