November 18: ORD

Today is November 18th. It's the 322nd day of the year. 43 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 33.

On the warm side, in 1979 the high was 71 with a low of 44. Two decades later, in 1999, history repeated as the high was again 71 with a low of 44. In 1991 the high was 67 with a low of 44. A decade after that, in 2001, the high was 63 with a low of 48. In 1985 the high was 60 with a low of 50. In 2004 the high was 61 (our most recent 60s high) with a low of 49. The year prior, in 2003, the high was 61 with a low of 48. The other warm high was 60 in 1998. The record high of 72 was set in 1953 at Midway. The record warmest low of 55 occurred back in 1941, at a time when the official readings were taken adjacent to Lake Michigan. 30 of the past 33 highs (91%) were in the: 30s (7), 40s (10), 50s (7) and 60s (6). All of the 50s highs occurred from 1978 to 1994. Two highs were in the warm 70s, the only 70s in O'Hare's history to date. One high was in the cold 20s.

In looking back through the years to the first November at O'Hare in 1958, the following instances were notable: in 1976 the high was 58 with a low of 26, a 32 degree spread. In 1975 the high was 68 with a low of 44, a warm day. In 1973 the high was a warm 60 with a low of 43, a warm day. In 1972 the high was a cold 35 with a low of 32, a three degree spread. In 1971 the high was 61 with a low of 43, a warm day. In 1969 the high was 55, then the temperature began falling to a low of 15 degrees on the 20th, a 40 degree plunge. In 1968 the high was 39 with a low of 34, a five degree spread. In 1965 the low was a cold 20 degrees. In 1959 the high was 32 with a low of 13, a cold day.

More recently, there were no large spreads. There were small spreads of four degrees two years ago in 2009 (47/43), five degrees in 1995 (39/34), six degrees in 1992 (41/35), six degrees in 1996 (34/28) and six degrees in 2007 (43/37).

On the cold side, in 1989 the high was 26 (O'Hare's only 20s high for the date) with a low of 15, our only 10s low since 1978. There was another 10s low prior to 1978. That was 13 in 1959. In 2000 the high was 32 with a low of 21. Three years ago, in 2008, the high was 34 with a low of 21. The other cold high was 34 in 1996. The record low of 8 was set way back in 1880. The record coldest high of 22 occurred way back in 1903. Both records occurred at a time when the official readings were taken adjacent to Lake Michigan. 24 of the last 33 lows (73%) were in the: 20s (12) and 30s (12). One low was in the cold 10s (a.k.a. teens). Eight lows (24%) were in the warm: 40s (7) and 50s (1).

There was an instance of a warm year followed by a cold year and then back to a warm year. In 1999 the high was 71 with a low of 44, overall 18.5 degrees ABOVE normal. Then in 2000 the high was 32 with a low of 21, overall 12.5 degrees BELOW normal. Then in 2001 the high was 63 with a low of 48, overall 16.5 degrees ABOVE normal. We had back to back very warm years. In 2003 it was 15.5 degrees above normal (61/48) and in 2004 it was 16 degrees above normal (61/49).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:17 and sunrise is at 6:47. Sunset is at 16:29 and twilight ends at 17:00. There's a total of 9 hours, 42 minutes of daylight today and 10 hours, 43 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:18 and sunrise is at 6:48. The moon reaches last quarter this morning at 9:09. Illumination was 54% at midnight, will be 49% at noon and 43% at midnight tonight. Moonset is at 12:23 this afternoon. Moonrise is at 0:02 tomorrow morning. Moonset is at 12:52 tomorrow afternoon. Moonlight time is 12 hours, 23 minutes which is 37 minutes shorter 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 six days.