October 25: ORD

Today is October 25th. It's the 298th day of the year. 67 days remain. It's week 43 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. Before this, the official site was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 59 and the normal low is 40. I've calculated the 32-year averages at 57 and 39.

On the warm side, in 1989 the high was 77 with a low of 52. Last year, in 2010, the high was 72 with a low of 56. In 2000 the high was 69 with a low of 55. The other warm high was 75 in 2004. The other warm low was 52 in 1986. The record high of 79 and record warmest low of 62 were set in on the same warm day in 1963 at Midway. 27 of the past 32 highs (84%) were in the: 40s (7), 50s (10) and 60s (10). There were two stretches of highs in the 40s, 50s & 60s. The first was eight years from 1981 through 1988. The second was ten years from 1994 through 2003. Our most recent 40s high was 47 in 2002. Four highs were in the warm 70s and one was in the cold 30s. Additionally, there was a cold high in the 30s prior to 1979 (38 in 1962). There were no 80s highs on this date in O'Hare's history or in the history of Chicago record-keeping.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1971 the high was 69 with a warm low of 59, a warm day. In 1967 the high was a cold 44 with a low of 38, a six degree spread. In 1966 the high was 57 with a cold low of 26, a 31 degree spread. In 1964 the high was a warm 76 with a low of 41, a 35 degree spread. In 1963 the high was a warm 77 with a low of 51, a warm day and year of the record high of 79 and record warmest low of 62 (records set at Midway). In 1962 the high was 38 with a low of 21, a cold day. In 1959 the high was a cold 40 with a low of 35, a five degree spread and cold day.

More recently, there was a large spread of 37 degrees in 2004 (75/38), 36 degrees in 1982 (62/26), 31 degrees in 1985 (67/36), 30 degrees in 1996 (68/38) and 30 degrees in 1999 (65/35). There were small spreads of three degrees in 1986 (55/52), four degrees in 1997 (49/45), five degrees in 1994 (46/41) and five degrees in 2002 (47/42).

On the cold side, in 1988 the high was 43 with a low of 26. In 1980 the high was 39 with a low of 33, a six degree spread. In 2001 the high was 40 with a low of 35, a five degree spread. In 1979 the high was 46 with a low of 31. The other cold low was 26 in 1982. The other cold highs were 45 in 1981, 46 in 1994 and 47 in 2002. The record low of 14 and record coldest high of 29 were set on the same cold day way back in 1887, a time when the official readings were taken adjacent to Lake Michigan. 24 of the last 32 lows (75%) were in the: 30s (14) and 40s (10). There were ten consecutive 30s & 40s lows from 1990 through 1999. Four lows were in the cold 20s and four were in the warm 50s. Our most recent 20s low was 27 in 2006. Our most recent 50s low of 56 was last year, in 2010.

There's two instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 1988 the high was 43 with a low of 26, overall 15.5 degrees BELOW normal. Then in 1989 the high was 77 with a low of 52, overall 14.5 degrees ABOVE normal. In the second instance, in 2000 the high was 69 with a low of 55, overall 12 degrees ABOVE normal. Then in 2001 the high was 40 with a low of 35, overall 12.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:49 and sunrise is at 7:18. Sunset is at 17:57 and twilight ends at 18:25. There's a total of 10 hours, 39 minutes of daylight today and 11 hours, 36 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:50 and sunrise is at 7:19. The moon is waning crescent and will be new tomorrow at 14:56. Illumination was 4% at midnight, will be 2% at noon and 1% at midnight tonight. Moonrise is at 5:50 this morning. Moonset is at 16:58 this afternoon. Moonrise is at 7:09 tomorrow morning. Moonlight time is 11 hours, 8 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. Halloween is in six days. Election Day is in 14 days.