September 19: ORD

Today is September 19th. It's the 262nd day of the year. 103 days remain. It's week 38 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 74 and the normal low is 53. I've calculated the 32-year averages at 75 and 55.

On the warm side, in 1985 the high was 87 with a low of 66. In 2002 the high was 80 with a low of 72. Two years earlier, in 2000, the high was 87 with a low of 62. Five years later, in 2005, the high was 84 with a low of 65. Two years later, in 2007, the high was 84 with a low of 65. Another warm high was 87 in 1984. The record high of 93 was set in 1955. The record warmest low of 74 occurred way back in 1908, a time when the official readings were taken adjacent to Lake Michigan. 23 of the past 32 highs (72%) were in the: 70s (10) and 80s (13). Nine highs were in the cool: 50s (2) and 60s (7). For 10 consecutive years, 1980 through 1989, highs were in the 70s & 80s. The four years following (1990-1993), highs were in the 50s & 60s. The next seven years, 1994-2000, highs were again in the 70s & 80s. From 2001-2010, except for a 55 degree high in 2006, there were three highs in each category (the 60s, 70s & 80s).

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1978 the high was 90 with a low of 67, a hot day. In 1976 the high was 82 with a low of 47, a 35 degree spread. In 1974 the high was a hot 87 degrees. In 1968 the high was a cool 62 with a low of 59, a three degree spread. In 1967 the low was a warm 65 degrees. In 1965 the high was 86 with a low of 68, a hot day. In 1963 the high was a hot 90 with a low of 63, a hot day. In 1962 the low was a cold 39 degrees, colder than the record low of 40.

More recently, there were large spreads of 34 degrees in 1984 (87/53), 33 degrees in 1999 (80/47) and 30 degrees in 1994 (85/55). There were no small spreads of up to seven degrees.

On the cool side, in 1991 the high was 56 with the record low of 40. In 2006 the high was 55 with a low of 47. The other cool high of 62 occurred in 1990. The record coolest high of 52 was set back in 1938, a time when the official readings were taken adjacent to Lake Michigan. 16 of the last 32 lows (50%) were in the 50s. Eight lows (25%) were in the cold 40s. Eight lows (25%) were in the warm: 60s (7) and 70s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:09 and sunrise is at 6:37. Sunset is at 18:56 and twilight ends at 19:24. There's a total of 12 hours, 19 minutes of daylight today and 13 hours, 15 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:10 and sunrise is at 6:38. The moon is waning gibbous and will reach last quarter tomorrow at 8:39. Illumination was 63% at midnight, will be 58% at noon and 53% at midnight tonight. Moonset is at 13:35 this afternoon. Moonrise is at 22:55 tonight. Moonset is at 14:24 tomorrow afternoon. Moonlight time is 14 hours, 40 minutes which is 4 minutes longer than yesterday.

Summer began June 4 and runs for 110 days through September 21. High temperatures in this period are usually in the 70s and 80s. Highs in the 60s, 90s and 100s occur infrequently. Columbus Day is in 21 days.