October 4: ORD

Today is October 4th. It's the 277th day of the year. 88 days remain. It's week 40 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 67 and the normal low is 46. I've calculated the 32-year averages at 65 and 45.

On the warm side, in 2005 the high was 87 with the record warmest low (and only 70s low) of 71. 2005 was the warmest October 4 in O'Hare's history. The previous warmest day was in 1967 when the high was also 87 but the low was a slightly cooler 66. The former record warmest low of 69 occurred in 1922. Also, that low of 71 tied October 1, 1971 as the warmest October low ever. In 2007 the high was 82 with a low of 51, a 31 degree spread. The record high of 90 was set in 1951. 17 of the past 32 highs (53%) were in the 60s. For seven consecutive years, from 1989 through 1995, highs were in the 60s. The past three years (2008-2010) have also featured highs in the 60s. Seven highs (22%) were in the warm: 70s (5) and 80s (2). Eight highs (25%) were in the 50s.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1976 the high was a warm 82 degrees. In 1975 the high was 75 with a low of 44, a 31 degree spread. In 1969 the high was 80 with a low of 61, a warm day. In 1967 the high was 87 with a low of 66, a hot day (the second hottest of the date). In 1965 the high was 57 with a cold low of 33, a cool day. In 1963 the high was 73 with a low of 41, a 32 degree spread. In 1959 the high was 60 with a low of 55, a five degree spread.

More recently, there were large spreads of 36 degrees in 1982 (77/41), 33 degrees in 1987 (69/36), 32 degrees in 1984 (70/38) and 31 degrees in 1993 (65/34). There were no small spreads of up to seven degrees.

On the cool side, in 1980 the high was 51 with the co-record low of 32. In 1988 the high was 52 with a low of 36. The other cold lows were the co-record low of 32 in 1989 and a low of 34 in 1993. The other cool high was 54 in 1999. 31 of the last 32 lows (97%) were in the: 30s (12), 40s (9) and 50s (10). One low was in the warm 70s (the record warmest low of 71, set in 2005). There have been no lows in the 60s over the last 32 years.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:25 and sunrise is at 6:53. Sunset is at 18:30 and twilight ends at 18:58. There's a total of 11 hours, 37 minutes of daylight today and 12 hours, 33 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:26 and sunrise is at 6:54. The moon is waxing gibbous, having reached first quarter last night at 22:15. Illumination was 51% at midnight, will be 57% at noon and 62% at midnight tonight. Moonrise is at 14:38 this afternoon. Moonset is at 0:34 tomorrow morning. Moonrise is at 15:14 tomorrow afternoon. Moonlight time is 9 hours, 22 minutes which is 12 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 six days.