December 26: ORD

Today is December 26th. It's the 360th day of the year. Five days remain. It's week 52 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. Observations have been official at O'Hare since Thursday, January 17, 1980. Before this, the official site was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 32 and the normal low is 18. I've calculated the 33-year averages at 30 and 16.

On the warm side, three years ago, in 2008, the high was 52 with a low of 24. In 1982 the high was 40 with a low of 33, a seven degree spread. The other warm highs were 47 in 1994, 45 in 1991, 45 in 2007 and 44 in 2003. The other warm low was 32 in 2005. The record high of 55 was set in 1971 at Midway and the record warmest low of 45 was set back in 1936, at a time when the official readings were taken adjacent to Lake Michigan. 13 of the past 33 highs (39%) were in the 30s. 14 highs (43%) were in the cold: 10s (a.k.a. teens) (7) and 20s (7). O'Hare's coldest high was 8 degrees in 1962. On the warm side, six highs (18%) were in the: 40s (5) and 50s (1). O'Hare also had a high of 52 in 1959. Along with the 52 degree high in 2008, these are O'Hare's warmest temperatures for the date.

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 13 with a low of -2, a cold day. In 1976 the low was a cold 5 degrees. In 1973 the high was 38 with a warm low of 35, a three degree spread and warm day. In 1971 the high was 44 with a low of 33, a warm day. 1971 was also the year of the record high of 55, set at Midway. In 1967 the high was 15 with a low of 0, a cold day. In 1966 the low was a cold 5 degrees. In 1964 the low was a cold 4 degrees. In 1962 the high was 8 with a low of -13, another cold day. That low of -13 is colder than the record low of -11 set in 1983. In 1961 the high was 30 with a low of 24, a six degree spread. In 1959 the high was 52 with a low of 42, a warm day.

More recently, we had small spreads of four degrees in 1986 (33/29), five degrees in 2005 (37/32), six degrees in 2006 (34/28), six degrees two years ago, in 2009 (26/20), seven degrees in 1979 (33/26) and seven degrees in 1997 (32/25).

On the cold side, in 1983 the high was 11 with the record low of -11. In 1990 the high was 12 with a low of -6. Three years later, in 1993, the high was 13 with a low of 6. In 2000 the high was 19 with a low of 3. In 1989 the high was 18 with a low of 5. In 2001 the high was 18 (our most recent 10s high) with a low of 9. The other cold lows were 2 in 1985 and 6 in 1992. The other cold high was 19 in 1996. The record coldest high of 5 was set back in 1925, at a time when the official readings were taken adjacent to Lake Michigan. 22 of the last 33 lows (67%) were in the: 10s (a.k.a. teens) (9) and 20s (13). On the cold side, nine highs (27%) were in the: negative 10s (1), negative single digits (1) and single digits (7). Our most recent single digit low was 9 degrees in 2001. O'Hare's coldest low was -13 in 1962. But since O'Hare was not the station of record at the time, that low of -13 is not the record low. O'Hare also had a low of -2 in 1977. On the warm side, two lows (6%) were in the 30s. O'Hare's warmest low was 42 in 1959.

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 1982 the high was 40 with a low of 33, overall 11.5 degrees ABOVE normal. Then in 1983 the high was 11 with a low of -11, overall 25 degrees BELOW normal. In the second instance, in 1993 the high was 13 with a low of 6, overall 15.5 degrees BELOW normal. Then in 1994 the high was 47 with a low of 24, overall 10.5 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:49 and sunrise is at 7:21. Sunset is at 16:27 and twilight ends at 16:59. There's a total of 9 hours, 6 minutes of daylight today and 10 hours, 10 minutes between twilights. Daylight time is the same as yesterday. Tomorrow twilight begins at 6:49 and sunrise is at 7:21. The moon is waxing crescent, having reached new two days ago at 12:06. Illumination was 3% at midnight, will be 5% at noon and 8% at midnight tonight. Moonrise is at 8:38 this morning. Moonset is at 18:57 tonight. Moonrise is at 9:13 tomorrow morning. Moonlight time is 10 hours, 19 minutes which is 28 minutes longer than yesterday.

Winter began December 1st and runs for 102 days through March 11th. High temperatures in this period are usually in the 20s and 30s. Highs in the 40s and 50s occur infrequently. New Year's Eve is in five days. New Year's Day is in six days.