July 24: ORD

Today is July 24th. It's the 205th day of the year. 160 days remain. It's week 30 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 84 and the normal low is 64. I've calculated the 31-year averages at 85 and 64.

On the hot side, in 2005 the high was 102 with the co-record warmest low of 78. The other co-record warmest low (78 degrees) occurred in 1940. Another warm low was 75 in 1987. Our second hottest high was 94 in 1999. The record high of 105 was set back in 1934, the hottest temperature ever recorded in Chicago's history. An interesting sidebar was that for ten straight years from 1989 to 1998, there were no highs of 90 or above. 19 of the last 31 highs (61%) were 80s. Eight highs were in the warmer: 90s (7) and 100s (1). Four highs were in the cooler 70s.

In looking back through the years to the first July at O'Hare in 1959, there were no notable instances of significantly hot or cool temperatures from 1959-1978.

More recently, there was a large temperature spread (diurnal) of 32 degrees in 1988 as the high was 91 with a low of 59.

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. In 2004 the high was just 71, the coolest high of the past 31 years. The record coolest high of 66 was set way, way back in 1896. Another cool high was 74 in 1992. The coolest low was the record low of 53 degrees, set in 2000. Other cool lows were 54 in 2003 and 55 in 2004. 17 of the last 31 lows were 60s. Eight lows were in the cooler 50s. Six lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 5:06 and sunrise was at 5:38. Sunset is at 20:21 and civil twilight ends at 20:53. Nautical twilight ends at 21:34 and astronomical twilight ends at 22:21. There's a total of 14 hours, 43 minutes of daylight today and 15 hours, 47 minutes between twilights. Tomorrow twilight begins at 5:07 and sunrise is at 5:39. The moon is waxing gibbous and will be completely full tomorrow night at 20:27 (the full Buck or Thunder moon). Illumination was 97% at midnight, will be 98% at noon and 99% at midnight tonight. Moonset was at 4:10 this morning. Moonrise is at 19:33 tonight. Moonset is at 5:12 tomorrow morning. Moonlight time is 8 hours, 37 minutes which is 22 minutes longer than yesterday.

Parent's Day is tomorrow. - Bernie -