August 12: ORD

Today is August 12th. It's the 224th day of the year. 141 days remain. It's week 32 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 82 and the normal low is 64. I've calculated the 32-year averages at 81 and 62.

On the hot side, in 1995 the high was 98 with a low of 75. In 1988 the high was 93 with a low of 75. Last year, in 2010, the high was 92 with a low of 74. The record high of 101 was set back in 1918. The record warmest low of 78 occurred way back in 1881. 27 of the past 32 highs (84%) were in the: 70s (12) and 80s (15). There were two long stretches of highs in the 70s or 80s. The first was nine years from 1979 through 1987. The second was eight years from 1996 through 2003. Three highs were in the hot 90s and two highs were in the cool 60s.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1977 the low was a cool 52 degrees. In 1967 the high was 74 with a cold low of 44, a 30 degree spread and cool day. That low of 44 was colder than the record low. In 1964 the high was a cool 66 with a low of 53, a cool day.

More recently, there were no large spreads of at least 30 degrees or small spreads of up to seven degrees diurnal.

On the cool side, in 2004 the high was the record coolest high of 62 with a low of 49. The previous record coolest high of 64 occurred way back in 1903. The official thermometer was located near Lake Michigan at the time. In 1982 the high was 74 with the record low of 47. In 1992 the high was 67 with a low of 56. Other cool lows were 50 degrees in both 1979 and 1986. 25 of the last 32 lows (78%) were in the: 50s (9) and 60s (16). Two lows were in the cold 40s. Five lows were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:27 and sunrise is at 5:57. Sunset is at 19:59 and twilight ends at 20:29. There's a total of 14 hours, 2 minutes of daylight today and 15 hours, 2 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:28 and sunrise is at 5:58. The moon is waxing gibbous and will be full tomorrow at 13:57 as the full Sturgeon moon. Other names for this moon are Green Corn and Grain. Illumination was 97% at midnight, will be 99% at noon and 100% at midnight tonight. Moonset is at 4:48 this morning. Moonrise is at 19:10 tonight. Moonset is at 5:53 tomorrow morning. Moonlight time is 9 hours, 38 minutes which is 33 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. Labor Day is in 24 days.