August 30: ORD

Today is August 30th. It's the 242nd day of the year. 123 days remain. It's week 35 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 80 and the normal low is 61. I've calculated the 32-year averages at 80 and 61.

On the hot side, in 1995 the high was 92 with a low of 74. Last year, in 2010, the high was 88 with a low of 74. The other 90s high was 90 in 1993. So the 90s highs occurred within two years of each other. The other 70s lows were 72 in 1983 and 71 (1980, 1991 and 2000). The record high of 96 was last set in 1953 after originally being set back in 1925. The record warmest low of 76 occurred back in 1932, having originally been set way back in 1881. 27 of the past 32 highs (84%) were in the: 70s (11) and 80s (16). Two highs were in the warm 90s and three were in the cool 60s (66 two years ago (in 2009), 67 in 1994 and 69 in 1999). There were two long streaks of highs in the 70s & 80s. The first was 22 years from 1971 through 1992 and then nine years from 2000 through 2008.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: in 1976 the high was 79 with a low of 49, a 30 degree spread. In 1967 the high was a cool 67 degrees. In 1965 the high was a cool 64 degrees. In 1962 the high was a hot 92 with a low of 62, a 30 degree spread. In 1959 the temperatures for yesterday (the 29th) and today (the 30th) were the same: a high of 86 with a low of 69.

More recently, there was a large spread of 31 degrees three years ago, in 2008 (87/51) and a small spread of six degrees in 1994 (67/61).

On the cool side, two years ago, in 2009, the high was 66 with a low of 51. In 1999 the high was 69 with a low of 55. The only other 60s high was 67 in 1994. In 1986 the high was 76 with a low of 48. The only other 40s low was 49 in 1988. So the 40s lows occurred within two years of each other. The record low of 47 was last set in 1946 after originally being set back in 1915. The record coolest high of 58 occurred way back in 1915. 24 of the last 32 lows (75%) were in the: 50s (13) and 60s (11). Two lows were in the cold 40s and six were in the warm 70s. For nine straight years, from 2001 through 2009, lows were in the 50s & 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:47 and sunrise is at 6:16. Sunset is at 19:31 and twilight ends at 20:00. There's a total of 13 hours, 15 minutes of daylight today and 14 hours, 13 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:48 and sunrise is at 6:17. The moon is waxing crescent, having passed new two nights ago at 22:04. Illumination was 2% at midnight, will be 4% at noon and 7% at midnight tonight. Moonrise is at 8:13 this morning. Moonset is at 20:02 tonight. Moonrise is at 9:29 tomorrow morning. Moonlight time is 11 hours, 49 minutes which is 45 minutes shorter 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. Labor Day is in six days. 9/11 Remembrance Day and Grandparents Day are in 11 days.