February 29: ORD

Today is February 29th. It's the 60th day of the year. 306 days remain. It's week 9 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 of record 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 40 and the normal low is 24. I've calculated the 8-year averages at 40 and 22.

On the warm side, in 2000 (O'Hare's warmest February 29th) the high was 64 (O'Hare's warmest high of the date) with the record warmest low of 44. In the next leap year, 2004, the high was 61 with a low of 32. The record high of 65 was set in 1972 at Midway. Four of the past eight highs (50%) were in the: 30s (3) and 40s (1). On the warm side, two highs (25%) were in the 60s. O'Hare's most recent and only 50s high of the date was 58 in 1976. On the cold side, two highs (25%) were in the: 10s (a.k.a. teens) (1) and 20s (1).

In looking back through the years to the first leap day at O'Hare in 1960, the following instances were notable: In 1976 the high was a warm 58 with a low of 35, a warm day. In 1972 the high was 62 with a low of 36, a warm day. In 1968 the high was 29 with a cold low of 12, a cold day. In 1960 the high was 18 with a low of 5, a cold day.

More recently, there were no small spreads of up to seven degrees or large spreads of at least 30 degrees.

On the cold side, in 1980 (O'Hare's coldest February 29th) the high was the record coldest high of 17 with a low of 0. In 1996 the high was 24 with a low of 10. The record low of -3 was set way back in 1884, at a time when the official readings were taken adjacent to Lake Michigan. Six of the last eight lows (75%) were in the: 10s (a.k.a. teens) (2), 20s (2) and 30s (2). One low (13%) was in the warm 40s. One low (12%) was in the cold single digits.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:01 and sunrise is at 6:29. Sunset is at 17:43 and twilight ends at 18:11. There's a total of 11 hours, 14 minutes of daylight today and 12 hours, 10 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:00 and sunrise is at 6:28. The moon reaches first quarter tonight at 19:21. Illumination was 42% at midnight, will be 47% at noon and 52% at midnight tonight. Moonset is at 0:38 this morning. Moonrise is at 10:12 this morning. Moonset is at 1:32 tomorrow morning. Moonlight time is 14 hours, 26 minutes which is four 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. St. Patrick's Day is in 17 days.