September 22: ORD

Today is September 22nd. It's the 265th day of the year. 100 days remain. It's week 38 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 72 and the normal low is 51. I've calculated the 32-year averages at 71 and 51.

On the warm side, in 1986 the high was 90 with a low of 65. In 2005 the high was 87 with a low of 63. Another hot high was 84 in 1980. The other two 80s highs occurred recently: 81 three years ago (in 2008) and 82 in 2004. The record high of 92 was set in 1956 at Midway. The record warmest low of 73 occurred way back in 1895, a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 32 highs (78%) were in the: 60s (11) and 70s (14). Our most recent 60s highs were 66 in 2002 and 69 in 2003. Five highs have been in the warm: 80s (4) and 90s (1). Two highs were in the cool 50s. For two periods of eight consecutive years, 1987-1994 and 1996-2003, highs were in the 60s & 70s.

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1976 the high was 71 with a cold low of 34 degrees, a 37 degree spread. In 1974 the high was 53 with a low of 32, a cold day. That low of 32 is equal to the record low. 1974 was also the year of the record coolest high of 49 at Midway. In 1970 the high was 68 with a low of 61, a seven degree spread. In 1968 the high was 83 with a warm low of 65, a warm day. In 1964 the low was a warm 64 degrees. In 1961 the high was 85 with a low of 63, a hot day. In 1959 the high was a 87 with a low of 65, a hot day.

More recently, there were large spreads of 35 degrees in 1989 (78/43), 32 degrees in 2004 (82/50) and 31 degrees in 1999 (72/41). There were no small spreads of up to seven degrees.

On the cool side, in 1995 the high was 52 with the record low of 32, our earliest fall freeze. In 1983 the high was 54 with a low of 37. The record coolest high of 49 was set in 1974 at Midway. 23 of the last 32 lows (72%) were in the: 40s (12) and 50s (11). Our most recent 40s low was 45 in 2002. Two lows were in the cold 30s and seven were in the warm 60s. For nine consecutive years, from 1996 through 2004, lows were in the 40s & 50s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:12 and sunrise is at 6:40. Sunset is at 18:51 and twilight ends at 19:19. There's a total of 12 hours, 11 minutes of daylight today and 13 hours, 7 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:13 and sunrise is at 6:41. The moon reached last quarter two days ago at 8:39 and is waning crescent. Illumination was 33% at midnight, will be 28% at noon and 23% at midnight tonight. Moonrise is at 0:56 this morning. Moonset is at 15:48 this afternoon. Moonrise is at 2:04 tomorrow morning. Moonlight time is 14 hours, 52 minutes which is 16 minutes shorter than the peak time yesterday.

Warm Fall begins today (September 22) and runs for 41 days through November 1. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 30s and 40s occur infrequently. Columbus Day is in 18 days.