February 23: ORD

Today is February 23rd. It's the 54th day of the year. 312 days remain. It's week 8 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. ORD has been the official site of record for Chicago 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 38 and the normal low is 23. I've calculated the 33-year averages at 39 and 24.

On the warm side, in 2000 the high was the record high of 66 (O'Hare's only 60s high of the date) with the record warmest low of 51 (O'Hare's only 50s low of the date). The former record high of 60 occurred in 1977 and the former record warmest low of 43 occurred in 1961. Both former records occurred at Midway International Airport. In 1984 the high was 59 with a low of 37. In 1996 the high was 54 with a low of 37. In 1985 the high was 50 with a low of 33. The other warm highs were 51 in 1995 and 50 in 1998 (our most recent 50s high). The other warm low was 37 in 2004, our most recent 30s low. 22 of the past 33 highs (67%) were in the: 30s (14) and 40s (8). On the warm side, six highs (18%) were in the: 50s (5) and 60s (1). On the cold side, five highs (15%) were in the 20s. O'Hare's pre-1979 warm days were 1977 (58/39) and 1961 (50/38).

In looking back through the years to the first February at O'Hare in 1959, the following instances were notable: In 1978 the high was a cold 26 with a low of 19, a seven degree spread. In 1977 the high was 58 with a low of 39, a warm day. In 1975 the high was 37 with a low of 33, a four degree spread. In 1974 the high was 22 with a low of 11, a cold day. In 1971 the high was 35 with a low of 31, a four degree spread. In 1969 the high was 40 with a warm low of 35, a five degree spread. In 1968 the high was 37 with a cold low of 7, a 30 degree spread. In 1967 the high was 23 with a low of 6, a cold day. In 1966 the high was 32 with a low of 25, a seven degree spread. In 1965 the high was 22 with a low of 10, a cold day. In 1963 the high was 22 with a low of 4, a cold day. In 1962 the high was 26 with a low of 8, a cold day. In 1961 the high was 50 with a low of 38, a warm day.

More recently, we had a spread of five degrees in 1981 as the high was 38 with a low of 33.

On the cold side, 1993 was O'Hare's coldest February 23rd, with a high of 20 and low of 2. In 1989 the high was 23 with a low of 4. Three years ago, in 2009, the high was 27 with a low of 9. The record low of -18 was set way back in 1873 and the record coldest high of -2 occurred way back in 1889. That high of -2 is the latest sub-zero high in Chicago's history, another suggestion that Winter is subsiding. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 23 of the last 33 lows (70%) were in the: 20s (13) and 30s (10). Nine lows (27%) were in the cold: single digits (3) and 10s (a.k.a. teens) (6). One low (3%) was in the warm 50s. There have been no lows in the 40s at O'Hare for the date.

Today is a major day in Chicago's snow history. In 1994, 5.1 inches fell. This was the second day of a four day stretch in which 16.1 inches fell. In 1965, 1.8 inches fell. This was the first of three days in which 10.0 inches fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:10 and sunrise is at 6:39. Sunset is at 17:35 and twilight ends at 18:04. There's a total of 10 hours, 56 minutes of daylight today and 11 hours, 54 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:09 and sunrise is at 6:37. The moon is waxing crescent, having passed new two days ago at 16:35. Illumination was 2% at midnight, will be 3% at noon and 5% at midnight tonight. Moonrise is at 7:03 this morning. Moonset is at 19:45 tonight. Moonrise is at 7:28 tomorrow morning. Moonlight time is 12 hours, 42 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. St. Patrick's Day is in 23 days.