July 29: ORD

Today is July 29th. It's the 210th day of the year. 155 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 63.

On the hot side, there were no days of a mean of at least 11.5 degrees above normal. The hottest temperatures were 97 in 1988, 96 in 1983, 96 in 1999 and 95 in 1995. The record high of 99 was set back in 1913. Warm lows were 74 in 2006 and 73 in 1990. The record warmest low of 85 occurred back in 1916. We had very high dew points in 1999. The top was 82 degrees, making 1999 perhaps the most humid July 29 on record. 16 of the last 31 highs were 80s. Seven highs were in the warmer 90s. Eight highs were in the cooler 70s.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1971 the low was a cool 52. In 1965 the high was 80 with a cool low of 50, a 30 degree spread. That low of 50 is the same as the record low. In 1962 the high was a cool 71 with a low of 54, a cool day.

More recently, there were large spreads of 30 degrees in both 1979 (88/58) and 1994 (82/52).

On the cool side, 1981 was the only day that had a mean of at least 11.5 degrees below normal. The high was 74 with a low of 51. The other cool lows were the record low of 50 in 1984 and 52 in 1994. Two other cool highs were 73 in 1992 and 74 in 1997. The record coolest high of 63 occurred way back in 1892. The official thermometer was located near Lake Michigan at the time. 18 of the last 31 lows were 60s. Eight lows were in the cooler 50s. Five lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 5:11 and sunrise was at 5:43. Sunset is at 20:16 and civil twilight ends at 20:48. Nautical twilight ends at 21:28 and astronomical twilight ends at 22:12. There's a total of 14 hours, 33 minutes of daylight today and 15 hours, 37 minutes between twilights. We are losing about two minutes of daylight a day. Tomorrow twilight begins at 5:12 and sunrise is at 5:44. The moon is waning gibbous. Illumination was 91% at midnight, will be 88% at noon and 85% at midnight tonight. Moonset was at 9:16 this morning. Moonrise is at 21:39 tonight. Moonset is at 10:15 tomorrow morning. Moonlight time is 11 hours, 37 minutes which is 39 minutes longer than yesterday. -Bernie-