December 28: ORD

Today is December 28th. It's the 362nd day of the year. Three 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 36 and 21.

On the warm side, in 1984 the high was the record high of 69 with the record warmest low of 49. In 2003 the high was 49 with a low of 41. In 1982 the high was 65 (the former record high) with a low of 21, a 44 degree spread. Note that the 60s highs occurred within two years of each other! In 2006 the high was 48 with a low of 36. In 1992 the high was 44 with a low of 34. A couple of years later, in 1994, the high was 42 with a low of 34. A couple of years after that, in 1996, the high was 39 with a low of 34, a spread of five degrees. In 2005 the temperatures were the same as in 1996, a high of 39 with a low of 34, also a spread of five degrees. The other warm lows were 32 in 1991, 30 in 1987 and 30 in 2007. 16 of the past 33 highs (49%) were in the 30s. On the warm side, nine highs (27%) were in the: 40s (7), 50s (0) and 60s (2). O'Hare's only 50s high (and warmest until 1982) was 50 in 1959. On the cold side, eight highs (24%) were in the: 10s (a.k.a. teens) (3) and 20s (5). O'Hare's coldest high was 10 in 1961. The other cold high was 18 in 1963. Both of these highs were colder than the three highs of 19 that O'Hare had in a six year span (in 1983, 1985 and 1988).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1977 the low was a cold 5 degrees. In 1976 the high was 23 with a cold low of 0, a cold day. In 1974 the high was 35 with a warm low of 33, a mere two degree spread. In 1969 the high was 32 with a low of 25, a seven degree spread. In 1963 the high was 18 with a low of -4, a cold day. In 1962 the high was 34 with a cold low of 1, a 33 degree spread. In 1961 the high was 10 with a low of -4, a cold day. In 1959 the high was 50 with a low of 34, a warm day. In 1958 the high was a warm 49 degrees with a low of 28, a warm day.

More recently, we had a small spread of four degrees in 2007 (high of 34, low of 30). The spreads were five degrees in 1987 (35/30) and in 1991 (37/32). There was a small spread of seven degrees in 1979 (31/24).

On the cold side, in 1983 the high was 19 with a low of -1. A couple of years later, in 1985, the high was 19 with a low of 0. In 2000 the high was 20 with a low of 6, our most recent 0s low. The other cold low was 3 in 1993. The other cold high was 19 in 1988. The record low of -13 was set back in 1924 and the record coldest high of -1 occurred way back in 1880. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 26 of the last 33 lows (79%) were in the: 10s (9), 20s (9) and 30s (8). On the cold side, five lows were in the: negative single digits (1) and single digits (4). O'Hare's coldest lows were -4 in both 1961 and 1963. On the warm side, two lows were in the warm 40s.

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 65 with a low of 21, overall 18 degrees ABOVE normal. Then in 1983 the high was 19 with a low of -1, overall 16 degrees BELOW normal. In the second instance, in 1984 the high was 69 with a low of 49, overall 34 degrees ABOVE normal. Then in 1985 the high was 19 with a low of 0, overall 15.5 degrees BELOW normal.

Today is a major snow day in O'Hare's history. Back in 1978, 2.8 inches fell. This was part of 16.8 inches that fell over four days.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:50 and sunrise is at 7:21. Sunset is at 16:28 and twilight ends at 17:00. There's a total of 9 hours, 7 minutes of daylight today and 10 hours, 10 minutes between twilights. Daylight time remained unchanged from yesterday. Tomorrow twilight begins at 6:50 and sunrise is at 7:22. The moon is waxing crescent. Illumination was 14% at midnight, will be 18% at noon and 22% at midnight tonight. Moonrise is at 9:42 this morning. Moonset is at 21:10 tonight. Moonrise is at 10:09 tomorrow morning. Moonlight time is 11 hours, 28 minutes which is 36 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 three days. New Year's Day is in four days.