July 17: ORD

Today is July 17th. It's the 198th day of the year. 167 days remain. It's week 29 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 86 and 66.

On the hot side, in 1982 the high was 93 with a low of 78. The only high that was significantly above normal was 97 in 2005. Some other 90s were: 95 in 2006, 94 in 1986 and 93 in 1983. The record high of 100 was set in 1942. The record warmest low of 80 occurred in 1878. 18 of the last 31 highs were 80s. Eight highs were in the warmer 90s and five highs were in the cooler 70s, including last year's high of 70 which, had it not made 70, would've been the first 60s high in the history of O'Hare on July 17. Through 2010, this is the average hottest day of the year.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1966 the high was 88 with a cool low of 51, a 37 degree spread.

More recently, there was a large spread of 34 degrees in 1989 (89/55).

On the cool side, in 1979 the high was 71 with a low of 50 (cooler than the record low) which is 51, set in 1985. The other cool high was 70 last year. The record coolest high of 64 occurred back in 1924. 17 of the last 31 lows were 60s. Five lows were in the cooler 50s. Nine lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 4:59 and sunrise was at 5:32. Sunset is at 20:27 and twilight ends at 21:00. There's a total of 14 hours, 55 minutes of daylight today and 16 hours, 1 minute between twilights. Tomorrow twilight begins at 5:00 and sunrise is at 5:33. The moon is waxing crescent and reaches first quarter tomorrow at 5:11. Illumination was 37% at midnight, will be 43% at noon and 48% at midnight tonight. Moonrise was at 12:45 this afternoon. Moonset is at 23:34 and moonrise is at 13:57 tomorrow. Moonlight time is 10 hours, 49 minutes which is 44 minutes shorter than yesterday.

Parent's Day is in eight days. - Bernie -