August 23: ORD

Today is August 23rd. It's the 235th day of the year. 130 days remain. It's week 34 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 80 and 62.

On the hot side, in 1998 the high was 90 with a low of 71 (our only 70s low). Five years earlier, in 1993, the high was 91 with a low of 69. Those were the only 90s highs over the past 32 years. The record high of 97 was set in 1947. The record warmest low of 76 occurred in 1968. 30 of the past 32 highs (94%) were in the: 70s (14) and 80s (16). Two highs were in the hot 90s.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1975 the low was a warm 74 degrees. In 1973 the high was a cool 67 with a low of 63, a four degree spread. In 1972 the high was 75 with a low of 71, a four degree spread. In 1969 the high was 86 with a low of 53, a 33 degree spread. In 1968 the high was 95 with a low of 77, a hot day and year of the record warmest low. In 1965 the high was 73 with a cold low of 47, a low colder than the record low. In 1964 the high was a cool 68 with a low of 52, a cool day. In 1962 the high was a hot 94 degrees. In 1961 the high was a cool 68 degrees.

More recently, there was a small spread of five degrees in 2001 (high of 74, low of 69).

On the cool side, in 1987 the high was 73 with a low of 54. Three years earlier, in 1984, the high was 74 with a low of 55. The record low is somewhat in dispute. The National Weather Service/Chicago (website) says that it's 51 degrees, set way back in 1888. However, in the daily summary for O'Hare, it says it's 48 degrees set way back in 1904. Our coolest high of 73 also occurred in 2005. The record coolest high of 62 occurred way back in 1890. The official thermometer was located near Lake Michigan at the time. 21 of the last 32 lows (66%) were in the 60s. Ten lows (31%) were in the cool 50s. One low (3%) was in the warm 70s (71 in 1998).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:39 and sunrise is at 6:09. Sunset is at 19:42 and twilight ends at 20:12. There's a total of 13 hours, 33 minutes of daylight today and 14 hours, 33 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:41 and sunrise is at 6:10. The moon is waning crescent, having passed last quarter two days ago at 16:54. Illumination was 37% at midnight, will be 32% at noon and 28% at midnight tonight. Moonrise is at 0:11 this morning. Moonset is at 15:44 this afternoon. Moonrise is at 1:05 tomorrow morning. Moonlight time is 15 hours, 33 minutes which is 42 minutes longer than yesterday. Moonlight time is at it's peak today.

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 13 days. 9/11 Remembrance Day and Grandparents Day are in 18 days.