Tuesday, July 28, 2009

July 27: ORD

Today is July 27th. It's the 208th day of the year. 157 days remain. It's week 30 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 84 and the normal low is 64. I've calculated the 30-year averages at 84 and 64.


On the hot side, there were no days of a mean of at least 11.5 degrees above normal. Two highs were the warmest at 93 degrees (1988 and 1989). The record high of 100 was set in 1916 and tied in 1955. The warmest lows were 70s. The warmest of the last 30 years was 73 in 1989.
The record warmest low of 82 occurred back in 1916. 17 of the last 30 highs were 80s. Five highs were in the warmer 90s. Eight highs were in the cooler: 60s (1) and 70s (7). There is an ongoing, 12 year sub-90 degree period that started in 1998 (through 2009).

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 19
77 the low was 52. In 1975 the high was 90. In 1972 the high was just 71. In 1970 the high was 90. In 1964 the high was 89 with a low of 59, a 30 degree spread. In 1962 the low was 51.

More recently, there w
as a small spread of six degrees in 1981 (69/63). The large spreads were 35 degrees in 1985 (87/52) and 33 degrees in 1979 (89/56).

On the cool side, threre were no days of a mean of at least 11.5 degrees below normal. The record low of 52 was set in 1985 and the record coolest high of 69 occurred in 1981. 15 of the last 30 lows were 60s. Nine lows were in the cooler 50s. Six lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:09 and sunrise is at 5:41. Sunset is at 20:18 and twilight ends at 20:50. Tomorrow twilight begins at 5:09 and sunrise is at 5:41. There's a total of 14 hours, 37 minutes of daylight today and 15 hours, 41 minutes between twilights. The moon is waxing crescent. Illumination was 33% at midnight, will be 38% at noon and 43% at midnight tonight. Moonrise is at 12:27 this afternoon. Moonset is at 23:02 tonight. Moonrise is at 13:36 tomorrow afternoon. Moonlight time is 10 hours, 35 minutes which is 44 minutes shorter than yesterday.

-Bernie-

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