September 28: ORD

Today is September 28th. It's the 271st day of the year. 94 days remain. It's week 39 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 70 and the normal low is 49. I've calculated the 32-year averages at 69 and 49.

On the warm side, in 1986 the high was 82 with our only 60s low of 65. A year later, in 1987, the high was 82 with a low of 56. The other warm high was 83 in 1979. Our most recent 80s high was 81 in 1995. The record high of 92 was set in 1953 and the record warmest low of 71 occurred in 1971. 21 of the past 32 highs (66%) were in the: 60s (12) and 70s (9). Five highs (15%) were in the warm 80s. Six highs (19%) 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 1975 the high was 73 with a low of 40, a 33 degree spread. In 1973 the low was a warm 64 degrees. In 1971 the high was 89 with a low of 73, a hot day and year of the record warmest low. In 1967 the high was a cool 53 with a low of 41, a cool day. In 1964 the high was 62 with a cold low of 32, a 30 degree spread and cool day. In 1963 the high was a hot 87 with a low of 53, a 34 degree spread. In 1961 the high was 56 with a low of 33, a cool day. In 1959 the high was 77 with a warm low of 64, a warm day.

More recently, there were large spreads of 32 degrees in 1979 (83/51), 32 degrees in 1989 (74/42) and 31 degrees in 1985 (76/45). There were small spreads of four degrees in 2001 (56/52) and seven degrees in 1988 (65/58).

On the cool side, in 1984 the high was 56 with a low of 36. Five years ago, in 2006, the high was 59 (our most recent 50s high) with a low of 40. Other cool highs were 58 in 2003 and 56 in 2001. The other cold low was 36 in 1991 (our most recent 30s low). The record low of 29 was set in 1942. The record coolest high of 50 was set way back in 1893. 28 of the last 32 lows (88%) were in the: 40s (12) and 50s (16). For an ongoing 19 consecutive years, beginning in 1992, lows were in the 40s & 50s. Three lows were in the cold 30s and one was in the warm 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:19 and sunrise is at 6:47. Sunset is at 18:40 and twilight ends at 19:08. There's a total of 11 hours, 53 minutes of daylight today and 12 hours, 49 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:20 and sunrise is at 6:48. The moon is waxing crescent, having passed new yesterday at 6:09. Illumination was 1% at midnight, will be 3% at noon and 5% at midnight tonight. Moonrise is at 8:21 this morning. Moonset is at 19:06 tonight. Moonrise is at 9:39 tomorrow morning. Moonlight time is 10 hours, 45 minutes which is 43 minutes shorter than yesterday.

Warm Fall began 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 12 days.