September 16: ORD

Today is September 16th. It's the 259th day of the year. 106 days remain. It's week 37 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.

According to the National Climatic Data Center (NCDC), the normal high is 75 and the normal low is 54. I've calculated the 32-year averages at 72 and 53.

On the warm side, in 1992 the high was 84 with a low of 70. Five years later, in 1997, the high was 85 with a low of 65. Three years before, in 1994, the high was 86 with a low of 63. Our other 80s highs were 85 in 1995 and 82 in 2003. The other warm lows were 66 in both 1987 and 1998. The record high of 92 was originally set in 1931 and tied in 1955. The record warmest low of 72 occurred back in 1907, a time when the official thermometer was located near Lake Michigan. 25 of the past 32 highs (78%) were in the: 60s (9) and 70s (16). Five highs were in the warm 80s and two were in the cool 50s.

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1973 the high was a cool 59 with a low of 52, a seven degree spread. Also in 1973, there was a mere 0.04 inches of rain but a big 1.32 inches on the following day, the 17th. There were also ten straight days of highs in the 70s (the 6th to the 15th). The month began with three 90s highs. In 1970 the high was a cool 63 degrees. In 1969 the high was 73 with a warm low of 66 degrees, a seven degree spread. In 1966 the high was 73 with a cold low of 40, a 33 degree spread. In 1965 the high was a cool 61 degrees. In 1963 the high was 85 with a low of 55, a 30 degree spread. In 1962 the high was 86 with a low of 48, a 38 degree spread. In 1959 the high was a cool 56 with a low of 47, a cool day and year of the record coolest high of 56.

More recently, there were large spreads of 34 degrees in 1985 (76/42), 32 degrees in 2003 (82/50) and 30 degrees in 1979 (77/47). There was a small spread of seven degrees in 1987 (73/66).

On the cool side, in 1984 the high was 64 with the record low of 37. Three years before, in 1981, the high was 59 with a low of 46. Other cool highs were 59 in 1993, 61 in 1982, 63 in 1986 and 63 in 1990. Another cold low was 42 in 1985. The record coolest high of 56 occurred in 1959. 25 of the last 32 lows (78%) were in the: 40s (12) and 50s (13). One low was in the cold 30s. Six lows were in the warm: 60s (5) and 70s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:06 and sunrise is at 6:34. Sunset is at 19:02 and twilight ends at 19:30. There's a total of 12 hours, 28 minutes of daylight today and 13 hours, 24 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:07 and sunrise is at 6:35. The moon is waning gibbous. Illumination was 87% at midnight, will be 84% at noon and 80% at midnight tonight. Moonset is at 10:46 this morning. Moonrise is at 20:45 tonight. Moonset is at 11:44 tomorrow morning. Moonlight time is 14 hours, 1 minute which is 27 minutes longer than yesterday.

Summer began June 4 and runs for 110 days through September 21. High temperatures in this period are usually in the 70s and 80s. Highs in the 60s, 90s and 100s occur infrequently. Citizenship Day is tomorrow.