December 31: ORD

Today is December 31st. It's the 365th day of the year. It's the last day of the year. 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 30 and the normal low is 16. I've calculated the 32-year averages at 34 and 21.

On the warm side, in 2006 the high was 56 with the record warmest low of 43. In 1933 the low was also just 43 degrees, so this is the record warmest low as well. In 2004 the high was 56 with a low of 29. These two highs of 56 were the warmest at O'Hare since 1965 when the high was 58. In 2002 the high was 41 with a low of 28. In 2005 the high was 37 with a low of 32, a five degree spread. Other warm highs were 44 in 1979 and 42 in 2003. Other warm lows were 32 (1980, 1995), 31 (1984, 1991), 30 in 1986 and 28 in 1989. The record high of 68 was set way back in 1875. 19 of the last 32 highs (59%) were 30s. On the warmer side, six highs were: 40s (4) and 50s (2). On the colder side, seven highs were: 10s (aka teens)(2) and 20s (5). Yesterday's high of 46 and low of 34 made it the 5th warmest of 33 years or in the top 15% of warm days for December 30th.

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 33 with a warm low of 30, a three degree spread. In 1976 the high was 6 with a low of -8, a cold day. 1976 had the record coolest high (5 at Midway). In 1974 the high was 36 with a warm low of 34, a two degree spread. In 1973 the high was 14 with a low of 2, a cold day. In 1970 the low was a warm 28. In 1968 the high was 15 with a low of -9, a cold day. In 1967 the high was 25 with a cold low of -11, a 36 degree spread, and cold day. That low of -11 was colder than the record low of -10 set the same day at Midway. In 1965 the high was 58 with a low of 30, a warm day. In 1963 the high was 17 with a low of -14, a 31 degree spread and cold day. That low of -14 was also colder than the record low. In 1961 the low was a cold 1 degree. In 1958 the high was 30 with a low of 24, a six degree spread.

More recently, we had small spreads of two degrees in 1980 (34/32), three degrees in 1991 (34/31), four degrees in 1995 (36/32), five degrees in 1984 (36/31), five degrees in 1989 (33/28) and six degrees in 1986 (36/30). We've had one large spread. It turned out to be a normal day. In 1987 the spread was 32 degrees as the high was 39 with a low of 7.

Six recent years in a row (2002-2007) were above normal. Four years ago (2006) was the warmest ever of the past 30 years, peaking at 56 degrees. This tied the same high of 56 in 2004. In 2004 that high of 56 occurred at 47 minutes past midnight.

On the cold side, in 1990 the high was 16 with a low of 1. In 1998 the high was 17 with a low of 9. In 1983 the high was 20 with a low of 6. The record low of -10 was set in 1967 at Midway (it was -11 at O'Hare). Even colder, it was -14 at O'Hare in 1963. The record coldest high of 5 was set in 1976 at Midway (it was 6 at O'Hare). 13 of the last 32 lows (41%) were 20s. On the colder side, 12 lows (37%) were: single digits (8) and 10s (aka teens)(4). On the warmer side, seven lows (22%) were: 30s (6) and 40s (1).

Today is a major snow day in O'Hare's history. Back in 1978, 10.1 inches fell. This was day four of a four day, 16.8 inch storm. The total snowfall of December 1978 was 35.3 inches at O'Hare. The Winter of 1978-79 was the snowiest ever, producing 80.6 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:50 and sunrise is at 7:22. Sunset is at 16:31 and twilight ends at 17:03. There's a total of 9 hours, 9 minutes of daylight today and 10 hours, 13 minutes between twilights. We are gaining a minute of daylight per day. Tomorrow twilight begins at 6:50 and sunrise is at 7:22. The moon is waning crescent. Illumination was 18% at midnight, will be 14% at noon and 11% at midnight tonight. Moonrise is at 3:50 this morning. Moonset is at 13:18 this afternoon. Moonrise is at 4:57 tomorrow morning. Moonlight time is 9 hours, 28 minutes which is 28 minutes less than yesterday.

New Year's Eve is today and New Year's Day is tomorrow. -Bernie-