August 10: ORD

Today is August 10th. It's the 222nd day of the year. 143 days remain. It's week 32 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 82 and 64.

On the hot side, there were no days of a mean of at least 11.5 degrees above normal. The warmest highs were in the 90s. It was 91 in both 1983 and 1992. It was 90 in 2005. The record high of 99 was set in 1944. The warmest low was 73 in 1988. The record warmest low of 79 occurred in 1938. Over the last 31 years, 18 highs were 80s. Three highs were in the warmer 90s. Ten highs were in the cooler: 60s (3) and 70s (7).

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1974 the high was 75 with a low of 72, a three degree spread. In 1967 the high was a cool 69 with a low of 53, a cool day. In 1966 the high was a cool 67 with a low of 61, a six degree spread. In 1965 the high was 70 with a low of 50, a cool day. In 1960 the high was a cool 68.

More recently, there was a large spread of 30 degrees in 2002 (89/59). The small spreads were five degrees in 2006 (79/74), seven degrees in 1988 (80/73) and seven degrees in 2004 (67/60).

On the cool side, in 1982 the high was 68 with the record low of 49. In 1994 the high was 67 with a low of 56. Another cool high was 67 in 2004. The record coolest high of 66 was set way back in 1882. The official thermometer was located near Lake Michigan at the time. Over the last 31 years, 20 lows were in the 60s. Six lows were in the cooler: 40s (1) and 50s (5). Five lows were in the warmer 70s, including three of the past four (70 last year and in '07 and 74 in '06).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 5:25 and sunrise was at 5:55. Sunset is at 20:01 and civil twilight ends at 20:32. Nautical twilight ends at 21:09 and astronomical twilight ends at 21:50. There's a total of 14 hours, 6 minutes of daylight today and 15 hours, 7 minutes between twilights. We are losing about three minutes of daylight a day. Tomorrow twilight begins at 5:26 and sunrise is at 5:57. The moon reached new last night at 22:08 and is waxing crescent. Illumination was 0% at midnight, will be 1% at noon and 2% at midnight tonight. Moonrise was at 6:35 this morning. Moonset is at 20:09 tonight. Moonrise is at 7:54 tomorrow morning. Moonlight time is 13 hours, 34 minutes which is 49 minutes shorter than yesterday. -Bernie-