November 17: ORD

Today is November 17th. It's the 321st day of the year. 44 days remain. It's week 46 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 47 and the normal low is 32. I've calculated the 33-year averages at 48 and 31.

On the warm side, in 2004 the high was 63 (our most recent 60s high) with a low of 54, our only 50s low since 1978. In 1979 the high was 69 with a low of 41. In 2001 the high was 66 with a low of 38. The other warm high was 64 in 1987. The other warm low was 44 two years ago, in 2009. The record high of 74 was set in 1975, previously in 1971 and originally 1952, all at Midway. The record warmest low of 60 occurred in 1952 at Midway. 22 of the past 33 highs (67%) were in the: 40s (13) and 50s (9). There were seven consecutive 40s & 50s highs from 1980 through 1986. Our most recent 50s high was 54 in 2003. Four highs (12%) were in the warm 60s. Seven highs (21%) were in the cold: 20s (1) and 30s (6). There have been no 70s highs since 1971.

In looking back through the years to the first November at O'Hare in 1958, the following instances were notable: in 1975 the high was 69 with a low of 49, a warm day and year of the record high of 74 at Midway. In 1972 the high was 36 with a low of 31, a five degree spread. In 1971 the high was 71 with a low of 50, a warm day. In 1969 the high was 51 with a warm low of 46, a five degree spread. In 1968 the high was 42 with a low of 39, a mere three degree spread. In 1966 the high was 66 with a low of 45, a warm day. In 1963 the high was 69 with a low of 55, a warm day. In 1961 the high was 36 with a low of 31, a five degree spread. In 1959 the high was 13 with a low of 2, a cold day and year of both the record low of 3 degrees and record coldest high of 14 at Midway. In 1958 the high was 71 with a low of 54, a warm day.

More recently, there were no large spreads. There were small spreads of three degrees two years ago in 2009 (47/44), five degrees in 2000 (32/27), six degrees in 1995 (38/32) and six degrees in 2006 (40/34).

On the cold side, in 2005 the high was 28 (ORD's only 20s high) with a low of 15. In 1989 the high was 34 with a low of 15. In 1997 the high was 34 with a low of 17. The other cold high was 32 in 2000. The record low of 3 and record coldest high of 14 were set on the same cold day in 1959 at Midway. 27 of the last 33 lows (82%) were in the: 20s (10) and 30s (17). There were three long streaks of 20s & 30s lows: 1. nine years from 1980-1988 2. seven years from 1990-1996 and 3. six years from 1998-2003. Three lows were in the cold 10s (a.k.a. teens). These 10s lows occurred between 1989 and 2005. Three lows were in the warm: 40s (2) and 50s (1). There were three more 50s lows prior to 1978.

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 2000 the high was 32 with a low of 27, overall 10.5 degrees BELOW normal. Then in 2001 the high was 66 with a low of 38, overall 12 degrees ABOVE normal. In the second instance, in 2004 the high was 63 with a low of 54, overall 18.5 degrees ABOVE normal. Then in 2005 the high was 28 with a low of 15, overall 18.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:16 and sunrise is at 6:46. Sunset is at 16:30 and twilight ends at 17:00. There's a total of 9 hours, 44 minutes of daylight today and 10 hours, 44 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:17 and sunrise is at 6:47. The moon is waning gibbous and will reach last quarter tomorrow morning at 9:09. Illumination was 65% at midnight, will be 60% at noon and 54% at midnight tonight. Moonset is at 11:53 this morning. Moonrise is at 22:53 tonight. Moonset is at 12:23 tomorrow afternoon. Moonlight time is 13 hours which is 34 minutes less than yesterday.

Cool Fall began November 2 and runs for 29 days through November 30. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 10s and 20s occur infrequently. Thanksgiving is in seven days.