September 1: ORD

Today is September 1st. It's the 244th day of the year. 121 days remain. It's week 35 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 78 and the normal low is 58. I've calculated the 31-year averages at 81 and 59.

On the hot side, in 2000 the high was 93 with a low of 67. Other 90s highs were 96 in 1984 and 90 two years ago. There were no 70s lows. The warmest lows were in the upper 60s (68 in 1979, 67 in 1990 and 67 in 2000). The record high of 101 was set in 1953. The record warmest low of 76 was set in 1973. Over the last 31 years, 16 highs were 80s. Three highs were in the warmer 90s. 12 highs were in the cooler: 60s (3) and 70s (9).

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 91 with a low of 73, a hot day and year of the record warmest low. In 1967 the high was 72 with a cool low of 41 (lower than the record low), a 31 degree spread and cool day. In 1966 the high was a hot 90 with a low of 60, a 30 degree spread. In 1963 the high was 82 with a low of 51, a 31 degree spread. In 1960 the high was 92 with a low of 73, a hot day.

More recently, there were large spreads of 39 degrees in 1984 (96/57), 30 degrees in 1997 (85/55) and 30 degrees in 1999 (85/55). There was a small spread of four degrees in 2003 (65/61).

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. There were three highs in the 60s (65 in 2003, 67 in 2001 and 68 in 1994). The coolest reading of 47 occurred last year. That was just the second 40s low in O'Hare's history. And there were three lows of 50 (1987, 1992 and 1994). The record low of 45 was set way back in 1901 and then tied in 1949. The record coolest high of 62 occurred back in 1909. Over the last 31 years, 15 lows were in the 50s and 15 lows were in the 60s. One low was in the 40s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:50 and sunrise is at 6:19. Sunset is at 19:27 and twilight ends at 19:56. There's a total of 13 hours, 8 minutes of daylight today and 14 hours, 6 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 5:51 and sunrise is at 6:20. The moon reaches last quarter today at 12:22. Illumination was 55% at midnight, will be 50% at noon and 45% at midnight tonight. Moonset is at 14:20 this afternoon and moonrise is at 23:25 tonight. Moonset is at 15:17 tomorrow afternoon. Moonlight time is 14 hours, 55 minutes which is 13 minutes longer than yesterday.

Labor Day is in five days and Patriot Day is in ten days. -Bernie-