August 27: ORD

Today is August 27th. It's the 239th day of the year. 126 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 81 and the normal low is 62. I've calculated the 32-year averages at 81 and 63.

On the hot side, in 1990 the high was 93 with a low of 72. Three years later, in 1993, the high was 94 (our most recent 90s high) with a low of 70. The other 90s highs were 92 in 1991, 91 in 1980 and 90 in 1984. The other 70s lows were 71 in 1980, 71 in 2006 and 70 in 1991. The record high of 97 and record warmest low of 77 were set on the same hot day in 1973. The record high of 97 was originally set in 1948 and tied five years later (and two decades before the latest incarnation) in 1953. 16 of the past 32 highs (50%) were in the 80s. Five highs (16%) were in the warm 90s. 11 highs (34%) were in the cool: 60s (5) and 70s (6).

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: in 1977 the high was 92 with a warm low of 78, a hot day. In 1976 the high was 95 with a low of 74, a hot day. In 1973 the high was 95 with a low of 75, a hot day. 1973 was the year that the records were set at Midway Airport. In 1968 the high was 67 with a low of 50, a cool day. In 1967 the high was a cool 64 with a low of 55, a cool day. In 1964 the high was 85 with a low of 55, a 30 degree spread. In 1962 the high was 88 with a low of 51, a 37 degree spread. In 1961 the high was a hot 93 degrees.

More recently, there were small spreads of five degrees in 1987 (66/61) and six degrees two years ago, in 2009 (67/61).

On the cool side, in 1986 the high was 67 with a low of 48. In 1992 the high was 63 with a low of 55. A decade earlier, in 1982, the high was 71 with the record low of 47. The other cool highs were 66 in 1987, 67 two years ago (in 2009) and 69 in 1988. The record coolest high of 61 occurred way back in 1915. 22 of the last 32 lows (69%) were in the 60s. Five lows (15%) were in the cool: 40s (2) and 50s (3). As you can see, the two 40s lows occurred quite some time ago. Our most recent 50s low was 59 degrees last year. Five lows (16%) were in the warm 70s, most recently 71 degrees in 2006.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:44 and sunrise is at 6:13. Sunset is at 19:36 and twilight ends at 20:05. There's a total of 13 hours, 23 minutes of daylight today and 14 hours, 21 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:45 and sunrise is at 6:14. The moon is waning crescent and new tomorrow at 22:04. Illumination was 5% at midnight, will be 3% at noon and 1% at midnight tonight. Moonrise is at 4:27 this morning. Moonset is at 18:29 tonight. Moonrise is at 5:41 tomorrow morning. Moonlight time is 14 hours, 2 minutes which is 38 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 nine days. 9/11 Remembrance Day and Grandparents Day are in 14 days.