June 27: ORD

Today is June 27th. It's the 179th day of the year. 187 days remain. It's week 26 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 83 and the normal low is 62. I've calculated the 33-year averages at 83 and 62.

On the hot side, in 1998 the high was 95 with a low of 69. In 2005 the high was 95 with a low of 68. Those highs of 95 were O'Hare's hottest since 1971. The record high of 101 was set in 1971 at Midway. The record warmest low of 79 occurred back in 1931 at the University of Chicago. 23 of the past 33 highs (70%) were in the 80s. Four highs (12%) were in the hot 90s. Six highs (18%) were in the cool: 60s (1) and 70s (5). Our most recent 70s high was 77 in 2000. The lone 60s high was 69. It occurred on the coolest day of the past 33 years in 1992. It didn't rain that day, but winds were Northeast, off the lake. The prior year, 1991, saw one of our hottest highs of 93 degrees. O'Hare's warmest June 27th was in 1959 as the high was 91 with a low of 75 (O'Hare's warmest low of the date). O'Hare's second warmest June 27th was in 1971 as the high was 96 (O'Hare's hottest high of the date) with a low of 69.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1971 the high was a hot 96 degrees. 1971 was the year of the record high of 101 at Midway. In 1968 the high was a cool 58 with a low of 55, a three degree spread and cool day. In 1959 the low was a warm 75 degrees.

The June 1964 heat wave was impressive. The following were the highs and lows: 26th (90/65), 27th (90/61), 28th (91/61), 29th (91/62) and 30th (90/61).

More recently, the spreads were all large: 32 degrees in 1981 (81/49) and 30 degrees in 1996 (89/59).

On the cool side, in 1992 (O'Hare's second coolest June 27th) the high was O'Hare's only 60s high of the date of 69 with the record low of 47. In 1988 the high was 78 with a low of 51. The prior year, 1987, saw a high of 75 with a low of 54. The only other 40s low was 49 in 1981. The record coolest high of 57 occurred way back in 1905, at a time when the official readings were taken adjacent to Lake Michigan. 28 of the last 33 lows (85%) were in the: 50s (10) and 60s (18). Our most recent 50s lows were 57 in 2003 and 53 in 2004. Two lows were in the cold 40s and three were in the warm 70s. The 70s lows (excluding 1959) occurred more recently (70 in 1999, 71 in 2007 and 72 in 2010). O'Hare's coolest June 27th was in 1968 as the high was 58 (O'Hare's coolest high of the date) with a low of 55, a mere three degree spread.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:44 and sunrise is at 5:19. Sunset is at 20:34 and twilight ends at 21:08. There's a total of 15 hours, 15 minutes of daylight today and 16 hours, 24 minutes between twilights. We lost no minutes of daylight from yesterday. Tomorrow twilight begins at 4:45 and sunrise is at 5:20. The moon is waxing gibbous, having reached first quarter last night at 22:30. Illumination was 51% at midnight, will be 57% at noon and 63% at midnight tonight. Moonset was at 0:23 this morning. Moonrise is at 13:52 this afternoon. Moonset is at 0:56 tomorrow morning. Moonlight time is 10 hours, 31 minutes which is 46 minutes shorter 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. Independence Day is in seven days.