August 21: ORD

Today is August 21st. It's the 233rd day of the year. 132 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 61. I've calculated the 31-year averages at 82 and 61.

On the hot side, in 2003 the high was 95 with a low of 72. The other 90s highs were 95 in 1983 and 90 in 1996. The record high of 99 was set in 1955. The only other 70s low was 70 in 1998. The record warmest low of 82 occurred back in 1916. Over the last 31 years, 28 highs (90%) were: 70s (11) and 80s (17). Three highs was in the warmer 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 94 with a low of 76, a hot day. In 1972 the low was a warm 74. In 1968 the high was 95 with a low of 77, a hot day. In 1962 the high was 90 with a low of 60, a 30 degree spread. In 1961 the low was a cool 48. In 1959 the high was 94 with a low of 75, a hot day.

More recently, there was a small spread of four degrees in 1990 (71/67). There were two large spreads: 32 degrees in 1991 (85/53) and 32 degrees in 1992 (81/49).

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. The coolest temperature was 49 in 1992. The coolest high was 71 in 1990. The record low of 46 was set back in 1950. The record coolest high of 66 was set back in 1939. Over the last 31 years, 28 lows (90%) were: 50s (14) and 60s (14). One low was in the cooler 40s and two lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 5:37 and sunrise was at 6:07. Sunset is at 19:45 and twilight ends at 20:15. There's a total of 13 hours, 38 minutes of daylight today and 14 hours, 38 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 5:39 and sunrise is at 6:08. The moon is waxing gibbous. Illumination was 89% at midnight, will be 92% at noon and 95% at midnight tonight. Moonset was at 3:05 this morning. Moonrise is at 18:08 this afternoon. Moonset is at 4:07 tomorrow morning. Moonlight time is 8 hours, 57 minutes which is 27 minutes longer than yesterday. -Bernie-