August 13: ORD

Today is August 13th. It's the 225th day of the year. 140 days remain. It's week 33 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 82 and the normal low is 63. I've calculated the 31-year averages at 81 and 63.

On the hot side, in 1995 the high was 96 with the co-record warmest low of 77. In 1988 the high was 91 with the co-record warmest low of 77. There were only two other 70s lows: 70 in both 1985 and 1994. The record high of 98 was set in 1944. Over the last 31 years, 18 highs were in the 80s. Ten highs were in the 70s. Two highs were in the warmer 90s and one high was in the cooler 60s.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1974 on the 13th & 14th, the temperatures were the same: a high of 78 with a low of 64. In 1967 the high was 77 with a cool low of 42, a 35 degree spread and cool day. That low of 42 was cooler than the record low. In 1964 the high was 70 with a low of 45, a cool day. That low of 45 was also cooler than the record low. In 1961 the high was 81 with a low of 48, a 33 degree spread. That low of 48 was also cooler than the record low.

More recently, there was a small spread of seven degrees in 2005 (75/68).

On the cool side, there were no means of at least 11.5 degrees below normal. The coolest days were 2004: a high of 71 and low of 51 (the co-record low) and in 1992: a high of 69 (our coolest high) with a low of 54. The other co-record low was 51 in 1982. The record coolest high of 64 was set way back in 1883. The official thermometer was located near Lake Michigan at the time. Over the last 31 years, 17 lows were 60s. Ten lows were in the cooler 50s. Four lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:28 and sunrise is at 5:59. Sunset is at 19:57 and civil twilight ends at 20:27. Nautical twilight ends at 21:04 and astronomical twilight ends at 21:45. There's a total of 13 hours, 58 minutes of daylight today and 14 hours, 59 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 5:29 and sunrise is at 6:00. The moon is waxing crescent. Illumination was 14% at midnight, will be 19% at noon and 23% at midnight tonight. Moonrise was at 10:28 this morning. Moonset is at 21:35 tonight. Moonrise is at 11:43 tomorrow morning. Moonlight time is 11 hours, 7 minutes which is 47 minutes shorter than yesterday. -Bernie-