December 27: ORD

Today is December 27th. It's the 361st day of the year. Four 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.

According to the National Climatic Data Center (NCDC), the normal high is 31 and the normal low is 17. The 31-year averages are 35 and 20.

On the warm side, in 1982 the high was the record high of 61 with a low of 40. Last year the high tied the record at 61 degrees with a low of 32. Also last year, I wrote the following: As I write this, we are experiencing a thunderstorm (heavy rain and lots of wind). In 1994 the high was 51 with a low of 29. A decade before that, in 1984, the high was 49 with a low of 30. In 2005 the high was 47 with a low of 32. Two years before that, in 2003, the high was 49 with a low of 28. A dozen years earlier, in 1991, the high was 37 with a low of 34, a three degree spread. Seven years later, in 1998, the high was 45 with a low of 26. Another warm low was 30 two years ago. The record warmest low of 51 was set in 1959. 20 of the last 31 highs were: 20s (9) and 30s (11). On the warmer side, eight highs were: 40s (5), 50s (1) and 60s (2). On the colder side, three highs were 10s (aka teens).

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 9 with a low of -2, a cold day. In 1975 the high was 26 with a low of 22, a four degree spread. In 1974 the high was 34 with a low of 29, a five degree spread. In 1973 the high was 35 with a low of 30, a five degree spread. In 1971 the high was a warm 47 degrees. In 1968 the high was 43 with a low of 34, a warm day. In 1963 the low was a cold 3 degrees. In 1962 the high was 25 with a low of -1, a cold day. In 1959 the high was 57 with a low of 50, a seven degree spread and warm day. In 1958 the high was 44 with a low of 32, a warm day.

More recently, we haven't had any spreads of seven degrees or less (except for 1991 (see above)) or anything 30 degrees or more.

On the cold side, in 2000 the high was 17 with a low of 6. 15 years earlier, in 1985, the high was 22 with a low of 3. Seven years before, in 1978, the high was 22 with a low of 3. Other cold highs were 18 in 1993 and 19 in 1983. The record low of -10 was set in 1950 and the record coldest high of 3 was set in 1925. 18 of the last 31 lows were: 10s (aka teens) (10) and 20s (8). On the colder side, seven lows were in the single digits. On the warmer side, six lows were: 30s (5) and 40s (1).

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 16:28 and twilight ends at 17:00. There's a total of 9 hours, 7 minutes of daylight today and 10 hours, 11 minutes between twilights. Tomorrow twilight begins at 6:50 and sunrise is at 7:22. The moon is waxing gibbous. Illumination was 75% at midnight, will be 79% at noon and 84% at midnight tonight. Moonset was at 2:51 and moonrise is at 12:44. Moonset is at 4:02 tomorrow morning. Moonlight time is 14 hours, 7 minutes which is 37 minutes more than yesterday.

Today is a major snow day in O'Hare's history. Back in 1894 in Chicago at the Auditorium Tower, which was the official reporting site for Chicago, 10.1 inches of snow fell. Back in 1978 tomorrow a major four-day snow of 16.8 inches began. But more on that tomorrow.