July 3: ORD

Today is July 3rd. It's the 184th day of the year. 181 days remain. It's week 27 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 83 and the normal low is 61. I've calculated the 31-year averages at 83 and 62.

On the hot side, in 1999 the high was 92 with a low of 76. In 2002 the high was 94 with a low of 73. There were three more 90s highs: 93 in 2003, 91 in 1991 and 91 in 1993. The record high of 102 was set in 1949. The record warmest low of 78 occurred back in 1911. 26 of the last 31 highs were: 70s (10) and 80s (16). Five highs were in the warmer 90s. One temperature quirk was that back in 1935, this was the date of the first high of 85 degrees or more for that year! Official readings were taken at the University of Chicago at the time.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1974 the high was 94 with a low of 74, a hot day. In 1971 the high was 87 with a low of 57, a 30 degree spread. In 1968 the low was a cool 48, cooler than the record low. In 1967 the high was a cool 71. In 1963 the high was 67 with a low of 48, a cool day. That low of 48, like in 1968, was cooler than the record low.

More recently, there were large spreads of: 34 degrees in 1988 (86/52), 32 degrees in 2005 (86/54), 30 degrees in 1979 (85/55), 30 degrees in 1980 (80/50) and 30 degrees in 1985 (83/53).

On the cool side, no days had means of at least 11.5 degrees below normal. The coolest lows were: the record low of 50 which occurred in 1980 and runner-up lows of 52 in 1986 and 1988. Midway never had a lower temperature and the lakefront kept prior official readings in Chicago a bit warmer. The coolest high was 71 two years ago (in 2008). The record coolest high of 63 occurred way back in 1909. 28 of the last 31 lows (90%) were: 50s (11) and 60s (17). Three lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 4:47 and sunrise was at 5:21. Sunset is at 20:33 and twilight ends at 21:07. There's a total of 15 hours, 12 minutes of daylight today and 16 hours, 20 minutes between twilights. Tomorrow twilight begins at 4:48 and sunrise is at 5:22. The moon is waning gibbous and reaches last quarter tomorrow morning at 9:35. Illumination was 63% at midnight, will be 58% at noon and 54% at midnight tonight. Moonset is at 12:25 this afternoon. Moonrise is at 23:56 tonight and moonset is at 13:26 tomorrow afternoon. Moonlight time is 12 hours, 29 minutes which is 38 minutes longer than yesterday. Moonlight time increases as the moon wanes, an inverse.

Independence Day is tomorrow. - Bernie -