August 24: ORD

Today is August 24rd. It's the 236th day of the year. 129 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 81 and 62.

On the hot side, in 1992 the high was 88 with a low of 69. Two years later, in 1994, the high was 87 with a low of 69. The year prior, 1993, the high was 87 with a low of 68. The only 90s high was 90 in 1983. The record high of 100 was set in 1947. There have been no 70s lows. The only other low of 69 occurred in 2007. The record warmest low of 78 occurred in 1975 at Midway. 19 the past 32 highs (59%) were in the 80s. 12 highs (38%) were in the cool 70s. One high (3%) was 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 high was 91 with a warm low of 79, a hot day and year of the record warmest low. That low of 79 is warmer than the record warmest low of 78 and is our most recent 70s low. In 1971 the high was 90 with a low of 59, a 31 degree spread. In 1969 the high was 87 with a low of 57, a 30 degree spread. In 1967 the low was a cold 48 degrees, equal to the record low. In 1966 the low was a cold 49 degrees, just above the record low. In 1965 the high was 82 with a cold low of 45, a 37 degree spread. That low of 45 is colder than the record low. In 1964 the high was 78 with a cold low of 45, a 33 degree spread. That low of 45 is also colder than the record low. In 1963 the high was 70 with a low of 66, a four degree spread. In 1962 the high was a hot 94 degrees.

More recently, there was a large spread of 31 degrees in 1983 (90/59). There were small spreads of six degrees in 1989 (73/67) and seven degrees in 1999 (74/67).

On the cool side, in 1987 the high was 72 (our coolest high) with a low of 51. Three years earlier, in 1984, the high was 76 with a low of 51. Those lows of 51 are the coolest of the last 32 years. The record low of 48 was set in 1942. The record coolest high of 63 occurred way back in 1891. The official thermometer was located near Lake Michigan at the time. 20 of the last 32 lows (63%) were in the 60s. 12 lows (37%) were in the cool 50s. Once again, there have been no lows in the 70s over the last 32 years. The most recent 70s low was 79 in 1975.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:41 and sunrise is at 6:10. Sunset is at 19:41 and twilight ends at 20:10. There's a total of 13 hours, 31 minutes of daylight today and 14 hours, 29 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:42 and sunrise is at 6:11. The moon is waning crescent. Illumination was 28% at midnight, will be 23% at noon and 19% at midnight tonight. Moonrise is at 1:05 this morning. Moonset is at 16:33 this afternoon. Moonrise is at 2:07 tomorrow morning. Moonlight time is 15 hours, 28 minutes which is 5 minutes shorter than yesterday. Moonlight time is near 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 12 days. 9/11 Remembrance Day and Grandparents Day are in 17 days.