July 8: ORD

Today is July 8th. It's the 190th day of the year. 176 days remain. It's week 28 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. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 84 and the normal low is 64. I've calculated the 33-year averages at 85 and 64.

On the hot side, in 1981 (O'Hare's warmest July 8th) the high was 94 with a low of 77 (O'Hare's warmest low of the date). In 2007 the high was 94 with a low of 75. O'Hare's hottest high of the date was 97 in 1988. The record high of 99 was set in 1955 at Midway. The record warmest low of 78 occurred way back in 1881, at a time when the official readings were taken adjacent to Lake Michigan. 18 of the past 33 highs (55%) were in the 80s. O'Hare recorded eight consecutive 80s highs from 1994 through 2001. Nine highs (27%) were in the hot 90s. Six highs (18%) were in the cool: 60s (1) and 70s (5). The lone 60s high occurred three years ago, in 2009, at 65 degrees. Our most recent 70s highs were 78 in 2003 and 76 in 2004.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1969 the high was a cool 71 degrees. In 1961 the high was 72 with a low of 51, a cool day.

More recently, there was a large spread of 32 degrees in 1983 (85/53).

On the cool side, in 1984 (O'Hare's coolest July 8th) the high was 74 with the record low of 48. Three years ago, in 2009 (O'Hare's third coolest July 8th), the high was 65 (O'Hare's coolest high of the date) with a low of 61, a small four degree spread. The record coolest high of 60 occurred way back in 1883, at a time when the official readings were taken adjacent to Lake Michigan. 17 of the last 33 lows (20%) were in the 60s. Nine lows (27%) were in the cool: 40s (1) and 50s (8). Seven lows (21%) were in the warm 70s. O'Hare's second coolest July 8th was in 1961 as the high was 72 with a low of 51.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:51 and sunrise is at 5:25. Sunset is at 20:31 and twilight ends at 21:05. There's a total of 15 hours, 6 minutes of daylight today and 16 hours, 14 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 4:52 and sunrise is at 5:26. The moon is waning gibbous. Illumination was 77% at midnight, will be 72% at noon and 68% at midnight tonight. Moonset is at 10:59 this morning. Moonrise is at 23:11 tonight. Moonset is at 12:01 tomorrow afternoon. Moonlight time is 11 hours, 48 minutes which is 37 minutes longer than yesterday.

Summer began on June 4th and runs for 110 days through September 21st. High temperatures in this period are usually in the 70s and 80s. Highs in the 90s and 100s occur infrequently. Parent's Day is in 14 days.