October 15: ORD

Today is October 15th. It's the 288th day of the year. 77 days remain. It's week 42 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 63 and the normal low is 43. I've calculated the 32-year averages at 63 and 44.

On the warm side, in 1989 the high was 83 (the only 80s high of the past 32 years and just the fourth 80s high in O'Hare's history on October 15th) with a low of 60 (our only 60s low). A year earlier, in 1988, the high was 76 with a low of 55. The other warm highs were 79 in 1999, 78 in 1996 and 75 in 1987. The record high of 88 was set in 1947 at Midway. The record warmest low of 69 occurred way back in 1897, at a time when the official readings were taken adjacent to Lake Michigan. 29 of the past 32 highs (91%) were in the: 50s (8), 60s (13) and 70s (8). Our most recent 70s high was 74 in 2007. One high was in the warm 80s and two were in the cold 40s.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1978 the high was 52 with a cold low of 31, a cool day. In 1972 the high was 51 with a low of 31, a cold day. In 1971 the high was a warm 77 degrees. In 1968 the high was 84 with a low of 67, a warm day. In 1965 the high was 74 with a warm low of 58, a warm day. In 1964 the high was 74 with a low of 33, a large 41 degree spread. In 1963 the high was a warm 84 with a low of 35, a huge 49 degree spread. In 1962 the high was 87 with a low of 64, a hot day. In 1961 the high was 71 with a low of 37, a 34 degree spread.

More recently, there were large spreads of 38 degrees in 1983 (73/35) and 31 degrees in 1999 (79/48). There were small spreads of two degrees in 1992 (51/49) and three degrees two years ago, in 2009 (44/41).

On the cool side, in 1991 the high was 49 with a low of 32. In 2006 the high was 52 with a low of 31. The other cool highs were 44 two years ago, in 2009 and 51 in 1992. The other cold low was 31 in 1997. The record low of 28 was set way back in 1876, at a time when the official readings were taken adjacent to Lake Michigan. The record coolest high of 44 first occurred in 1943 and was tied two years ago in 2009. 24 of the last 32 lows (75%) were in the: 30s (11) and 40s (13). Eight lows (25%) were in the warm: 50s (7) and 60s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:38 and sunrise is at 7:06. Sunset is at 18:12 and twilight ends at 18:40. There's a total of 11 hours, 6 minutes of daylight today and 12 hours, 2 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:39 and sunrise is at 7:07. The moon is waning gibbous. Illumination was 91% at midnight, will be 88% at noon and 85% at midnight tonight. Moonset is at 10:34 this morning. Moonrise is at 20:04 tonight. Moonset is at 11:29 tomorrow morning. Moonlight time is 14 hours, 30 minutes which is 16 minutes longer 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. United Nations Day is in nine days.