January 21: ORD

Today is January 21st. It's the 21st day of the year. 345 days remain. It's week 3 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 31 and the normal low is 16. I've calculated the 33-year averages at 30 and 16.

On the warm side, in 1986 the high was 54 (O'Hare's warmest high of the date) with a low of 30. In 1999 the high was 41 with a low of 32. Six years earlier, in 1993, the high was 38 with a low of 33, a five degree spread. The other warm high was 45 in 1997. The other warm lows were 30 two years ago (in 2010) and 29 in 1998. The record high of 62 was set way back in 1906 and the record warmest low of 43 was set back in 1916. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 23 of the past 33 highs (70%) were in the: 20s (9) and 30s (14). O'Hare had seven consecutive highs in the 20s & 30s from 2004 through 2010. Last year (2011) the high was 8. On the warm side, four highs (12%) were in the: 40s (3) and 50s (1). O'Hare had highs of 50 degrees in 1964 and 1967. On the cold side, six highs were in the: single digits (2) and 10s (a.k.a. teens) (4). O'Hare's coldest high was 3 in 1970. The most recent 10s high (a.k.a. teens) was 18 in 2003.

In looking back through the years to the first January at O'Hare in 1959, the following instances were notable: in 1976 the high was 26 with a low of 19, a seven degree spread. In 1974 the high was 37 with a warm low of 35, a two degree spread and warm day. In 1970 the high was 3 with a low of -15, a cold day. In 1969 the high was 40 with a warm low of 36, a four degree spread and warm day. In 1968 the high was a warm 43 degrees. In 1967 the high was 50 with a low of 35, another warm day and part of the pre-blizzard warm-up. In 1966 the high was 30 with a low of 25, a five degree spread. In 1964 the high was 50 with a low of 35, a warm day. In 1963 the high was 11 with a low of -17, a cold day. In 1961 the high was 12 with a low of -1, a cold day. In 1960 the high was a cold 17 with a low of 6, a cold day. In fact, the back-to-back days of yesterday and today in 1960 had the same high and low of 17 and 6.

More recently, we had small spreads of three degrees in 1998 (32/29) and 2007 (29/26). The spreads were five degrees in 1995 (26/21), five degrees two years ago, in 2010 (35/30), six degrees in 1988 (31/25), seven degrees in 1981 (32/25) and seven degrees in 2005 (24/17).

On the cold side, in 1984 the high was 6 with the record low of -22. Last year, in 2011, the high was 8 with a low of -4. In 2000 the high was 13 with a low of -3. In 1985 the high was 18 with a low of -6. In 1994 the high was 21 with a low of -5. Three years earlier, in 1991, the high was 17 with a low of 3. In 2003 the high was 18 with a low of 6. The record coldest high of -4 was set way back in 1883, at a time when the official readings were taken adjacent to Lake Michigan. 20 of the last 33 lows (61%) were in the: 10s (a.k.a. teens) (8) and 20s (12). On the cold side, nine lows (27%) were in the: negative 20s (1), negative single digits (4) and single digits (4). Four lows (12%) were in the warm 30s. O'Hare's warmest low was 36 in 1969. There have been no lows in the negative 10s (a.k.a. negative teens) since the low of -15 in 1970. O'Hare also had a low of -17 in 1963.

There were three instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 1985 the high was 18 with a low of -6, overall 18 degrees BELOW normal. Then in 1986 the high was 54 with a low of 30, overall 18 degrees ABOVE normal. In the second instance, in 1993 the high was 38 with a low of 33, overall 11.5 degrees ABOVE normal. Then in 1994 the high was 21 with a low of -5, overall 16 degrees BELOW normal. In the third instance, in 1999 the high was 41 with a low of 32, overall 12.5 degrees ABOVE normal. Then in 2000 the high was 13 with a low of -3, overall 19 degrees BELOW normal.

Today is a major day in O'Hare's snow history. In 2005, 4.8 inches fell. This was the second day of a four day, 12.7 inch period of snow. Along with the 9.8 inches that fell earlier on January 4-6, this comprised 22.5 inches or 81% of the month's total of 27.8 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:46 and sunrise is at 7:16. Sunset is at 16:53 and twilight ends at 17:24. There's a total of 9 hours, 37 minutes of daylight today and 10 hours, 38 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:45 and sunrise is at 7:16. The moon is waning crescent, two days from new. Illumination was 5% at midnight, will be 3% at noon and 1% at midnight tonight. Moonrise is at 5:48 this morning. Moonset is at 15:28 this afternoon. Moonrise is at 6:32 tomorrow morning. Moonlight time is 9 hours, 40 minutes which is 13 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. National Freedom Day is in 11 days. Groundhog Day is in 12 days.