January 18: ORD

Today is January 18th. It's the 18th day of the year. 348 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 28 and 12.

On the warm side, in 1986 the high was 45 with a low of 34. A decade later, in 1996, the high was the record high of 61 with a low of 13, a 48 degree spread. In 1996 the former record high of 57 (1933) was broken early in the morning before the temperature dropped 48 degrees. It was one of the worst temperature drops in Chicago's history. In 1989 the high was 45 with a low of 28. Six years later, in 1995, the high was 43 (our most recent 40s high) with a low of 29. In 1981 the high was 43 with a low of 26. The other warm low was 32 in 1988. The record warmest low of 47 was set in 1973 at Midway. 22 of the past 33 highs (67%) were in the: 20s (10) and 30s (12). On the warm side, five highs (15%) were in the: 40s (4) and 60s (1). The only 50s high for the date was 53 in 1973. On the cold side, six highs (18%) were in the: negative 10s (a.k.a. negative teens) (1), single digits (2) and 10s (a.k.a. teens) (3). Before 1979, O'Hare's only single digit high was 6 in 1962. There's been no highs in the negative single digits for the date in the history of O'Hare.

In looking back through the years to the first January at O'Hare in 1959, the following instances were notable: in 1977 the high was 23 with a cold low of -3, a cold day. In 1976 the high was 22 with a cold low of -7, a cold day. In 1975 the low was a warm 28 degrees. In 1974 the high was 42 with a warm low of 35, a seven degree spread and warm day. In 1973 the high was 53 with a low of 47, a six degree spread and a warm day. 1973 was also the year of the record warmest low of 47 at Midway. In 1972 the high was 47 with a low of 36, a warm day. In 1971 the high was 18 with a low of -1, a cold day. In 1970 the high was 11 with a low of -2, a cold day. In 1969 the high was 35 with a warm low of 30, a five degree spread. In 1968 the high was 38 with a warm low of 32, a six degree spread and warm day. In 1967 the high was 11 with a low of -11, a cold day. In 1966 the high was 11 with a low of -7, a cold day. In 1965 the high was 19 with a low of 1, a cold day. In 1964 the high was 48 with a low of 27, a warm day. In 1963 the low was a cold 4 degrees. In 1962 the high was 6 with a low of -6, a cold day. In 1960 the high was 32 with a low of 25, a seven degree spread. In 1959 the low was a cold -1 degrees.

On the cold side, in 1994 the high was the record coldest high of -11 with the record low of -21. That high of -11 tied the record for the coldest high ever with December 24, 1983. Other lows in 1994 were: Lake Villa: -26; Aurora, DeKalb and Marengo: -24; Rockford and Elgin: -23; Waukegan and Wheaton: -22; Midway: -20. A decade earlier, in 1984, the high was 8 with a low of -10. In 1997 the high was 6 with a low of -5. Five years earlier, in 1992, the high was 11 with a low of -1. In 1979 the high was 23 with a low of -8. Three years later, in 1982, the high was 19 with a low of 4. The other cold lows were 1 in 2005, 3 in 1983 and 4 in 1987. The other cold high was 17 three years ago, in 2009. 26 of the last 33 lows (79%) were in the: single digits (10), 10s (a.k.a. teens) (7) and 20s (9). Five lows were in the cold: negative 20s (1), negative 10s (a.k.a. negative teens) (1) and negative single digits (3). Prior to 1979, O'Hare's coldest low was -11 in 1967. Two lows were in the warm 30s. O'Hare's warmest low was 47 in 1973. Through Winter 2010-11, this is the average coldest day of the year.

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 1994 the high was -11 with a low of -21, overall 39 degrees BELOW normal. Then in 1995 the high was 43 with a low of 29, overall 13 degrees ABOVE normal. In the second instance, in 1996 the high was 61 with a low of 13, overall 14 degrees ABOVE normal. Then in 1997 the high was 6 with a low of -5, overall 22.5 degrees BELOW normal.

And now a note about the consecutive days of measurable snowfall record. The record (until January '09) was eight consecutive days set from December 13-20 in 1973. In January '09 we had nine. The amounts and days were: 6th (1.2), 7th (0.8), 8th (0.1), 9th (3.6), 10th (8.4), 11th (0.1), 12th (1.5), 13th (0.1) and 14th (2.2) for a total of 18 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:47 and sunrise is at 7:18. Sunset is at 16:49 and twilight ends at 17:20. There's a total of 9 hours, 31 minutes of daylight today and 10 hours, 33 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:47 and sunrise is at 7:18. The moon is waning crescent, having passed last quarter two days ago at 3:08. Illumination was 29% at midnight, will be 24% at noon and 20% at midnight tonight. Moonrise is at 2:48 this morning. Moonset is at 12:27 this afternoon. Moonrise is at 3:55 tomorrow morning. Moonlight time is 9 hours, 39 minutes which is 25 minutes shorter 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 14 days. Groundhog Day is in 15 days.