July 6: ORD

Today is July 6th. It's the 187th day of the year. 178 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 62. I've calculated the 32-year averages at 85 and 61.

On the hot side, in 1994 the high was 94 with a low of 72. In 1988 the high was the record high of 99 with a low of 66, a 33 degree spread. The record high of 99 was originally set in 1874. The mid 90s highs were 96 in 1991, 95 in 1989 and 94 in 1982. The record warmest low of 80 occurred in 1977. 16 of the past 32 highs (50%) were in the 80s. Eight highs (25%) were in the hot 90s. Eight highs (25%) were in the cool: 60s (1) and 70s (7). As you can see, 5 of the 8 highs in the 90s occurred from 1986 to 1991. Within this period, we experienced the roller-coaster effect. The high in 1989 was 95. The next year, 1990, the high was only 69 (our only 60s high). And the year after, in 1991, the high was 96. The high of 90 last year (in 2010) was our first 90s high since 1994 (16 years prior).

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1977 the high was 96 with a low of 78, a hot day and year of the record warmest low (80 at Midway). In 1969 the high was a cool 65 with a low of 61, a four degree spread. In 1968 the high was 81 with a cold low of 49, a 32 degree spread. In 1967 the high was 76 with a cold low of 46 (tied with the record), a 30 degree spread. In 1965 the high was 80 with a cold low of 42 (colder than the record), a 38 degree spread. In 1961 the high was 78 with a cold low of 48, a 30 degree spread.

More recently, there were large spreads of: 33 degrees in 1989 (95/62), 31 degrees in 2001 (81/50), 30 degrees in 1981 (88/58) and 30 degrees in 1996 (88/58).

On the cool side, in 1983 the high was 71 with the co-record low of 46. Four years earlier, in 1979, the high was 78 with a low of 43. That low of 43 was colder than the record low! These 40s lows were the only ones since 1979. The other co-record low is 46, set at Midway in 1979. Other cool lows were 50 in both 1984 and 2001. Another cool high was 69 in 1990. The record coolest high of 63 occurred way back in 1873. 26 of the last 32 lows (81%) were in the: 50s (11) and 60s (15). Two lows were in the cold 40s and four were in the warm 70s. The low of 73 last year, in 2010, was our first 70s low since 71 in 1999.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:49 and sunrise is at 5:24. Sunset is at 20:32 and twilight ends at 21:07. There's a total of 15 hours, 8 minutes of daylight today and 16 hours, 18 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 4:50 and sunrise is at 5:24. The moon is waxing crescent. Illumination was 28% at midnight, will be 33% at noon and 38% at midnight tonight. Moonrise is at 11:32 this morning. Moonset is at 23:28 tonight. Moonrise is at 12:44 tomorrow afternoon. Moonlight time is 11 hours, 56 minutes which is 44 minutes shorter than yesterday.

Summer began June 4 and runs for 110 days through September 21. High temperatures in this period are usually in the 70s and 80s. Highs in the 60s, 90s and 100s occur infrequently. Parent's Day is in 18 days.