June 6: ORD

Today is June 6th. It's the 158th day of the year. 208 days remain. It's week 23 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 77 and the normal low is 55. I've calculated the 33-year averages at 78 and 55.

On the hot side, in 1999 the high was 91 with a low of 69 (O'Hare's second warmest low of the date). In 2008 the high was 87 with a low of 73 (O'Hare's warmest low of the date). 1999 and 2008 are tied with 1971 as O'Hare's hottest June 6th. In 1971, the high was 92 (O'Hare's second warmest high of the date) with a low of 68. In 1984 the high was 89 with a low of 66. In 1988 the high was 91 with a low of 64. In 2005 the high was 89 with a low of 66. The other hot highs were 93 last year, in 2011 (O'Hare's hottest high of the date), 90 in 1979 and 90 in 1994. The record high of 97 was set in 1971 at Midway. The record warmest low of 77 occurred back in 1925, at a time when the official readings were taken adjacent to Lake Michigan. 21 of the past 33 highs (64%) were in the: 70s (9) and 80s (12). O'Hare recorded six consecutive highs in the 70s and 80s from 2003 through 2008. Five highs (15%) were in the hot 90s. Seven highs (21%) were in the cool 60s.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1976 the high was 84 with a low of 53, a 31 degree spread. In 1971 the high was 92 with a low of 68, the year of the record high and a hot day. 1971 had the same high and low (92 & 68) for yesterday (the 5th) and today. In 1968 the high was a hot 90 with a low of 66, a hot day. In 1963 the high was 90 with a low of 68, a hot day.

More recently, there were additional large spreads of 39 degrees in 1979 (90/51), 33 degrees in 1982 (73/40), 33 degrees in 1992 (83/50) and 33 degrees last year, in 2011 (93/60).

On the cool side, in 1998 (O'Hare's coolest June 6th by just half a degree) the high was 64 with a low of 43. In 1985 the high was 69 with the record (and only 30s) low of 39, a 30 degree spread. The other cool highs were 62 in 2001 (O'Hare's coolest high of the date), 63 three years ago (in 2009) and 65 in 1986. The other cold low was 40 in 1982. The record coolest high of 50 occurred way back in 1894, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the last 33 lows (76%) were in the: 50s (16) and 60s (9). O'Hare recorded seven consecutive 50s and 60s lows from 1986 through 1992. Of these, six of them (86%) were in the 50s. Seven lows (21%) were in the cold: 30s (1) and 40s (6). One low (3%) was in the warm 70s.

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In 1984 the high was 89 with a low of 66, overall 11.5 degrees ABOVE normal. Then in 1985 the high was 69 with a low of 39, overall 12 degrees BELOW normal. In the second instance, in 1998 the high was 64 with a low of 43, overall 12.5 degrees BELOW normal. Then in 1999 the high was 91 with a low of 69, overall 14 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:43 and sunrise is at 5:17. Sunset is at 20:27 and twilight ends at 21:01. There's a total of 15 hours, 10 minutes of daylight today and 16 hours, 18 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:43 and sunrise is at 5:17. The moon is waning gibbous, having passed the full Strawberry (a.k.a. Rose or Hot) moon two mornings ago at 6:12. Illumination was 95% at midnight, will be 93% at noon and 89% at midnight tonight. Moonset was at 7:40 this morning. Moonrise is at 22:36 tonight. Moonset is at 8:51 tomorrow morning. Moonlight time is 9 hours, 4 minutes which is 24 minutes longer than yesterday. 

Summer began two days ago, 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. Flag Day is in eight days.