September 25: ORD

Today is September 25th. It's the 268th day of the year. 97 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 71 and the normal low is 50. I've calculated the 31-year averages at 71 and 49.

On the warm side, in 1986 the high was 88 with a low of 68. Three years ago the high was 85 with a low of 63. Other warm lows were 67 in 2005 and 63 two years ago. The record high of 90 was set back in 1933 and the record warmest low of 72 occurred in 1920, a time when the official readings were taken on the lakefront. Over the last 31 years, 13 highs were in the 70s. Six highs were in the warmer 80s. 12 highs were in the cooler: 50s (5) and 60s (7).

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 a cool 59 with a low of 52, a seven degree spread. In 1973 the high was 80 with a warm low of 69, a warm day. In 1972 the high was 74 with a warm low of 68, a six degree spread. In 1971 the high was a cool 58 with a low of 51, a seven degree spread. In 1967 the high was 73 with a low of 40, a 33 degree spread. In 1964 the high was 74 with a low of 40, a 34 degree spread. In 1963 the high was a warm 83 with a low of 52, a 31 degree spread. In 1961 the high was a cool 56 with a low of 42, a cool day. In 1959 the high was 85 with a low of 63, a hot day.

More recently, there were large spreads of 37 degrees in 1999 (80/43), 34 degrees in 1984 (74/40), 32 degrees in 1988 (77/45), 31 degrees in 1989 (70/39), 31 degrees in 2002 (74/43) and 30 degrees in 1998 (81/51). There was a small spread of three degrees in 1983 (58/55).

On the cool side, in 1985 the high was 58 with a low of 35. In 2000 the high was 55 with a low of 43. In 2001 the high was 58 with a low of 40. In 1982 the high was 52 with a low of 47, a five degree spread. Another cool high was 58 in 1983. The record low of 30 and record coolest high of 46 were set on the same day in 1942. 15 of the last 31 lows were 40s. Two lows were in the cooler 30s. 14 lows were in the warmer: 50s (9) and 60s (5).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:16 and sunrise is at 6:44. Sunset is at 18:45 and twilight ends at 19:13. There's a total of 12 hours, 1 minute of daylight today and 12 hours, 57 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 6:17 and sunrise is at 6:45. The moon reached the full Harvest moon at 4:17 two days ago and is waning gibbous. Illumination was 97% at midnight, will be 95% at noon and 92% at midnight tonight. Moonset is at 9:03 this morning. Moonrise is at 19:26 tonight. Moonset is at 10:06 tomorrow morning. Moonlight time is 13 hours, 37 minutes which is 35 minutes longer than yesterday.

Columbus Day is in 16 days. -Bernie-