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 31-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. Back-to-back years had the highest temps at 93 degrees (1988 and 1989). The record high of 100 was set in 1916 and tied in 1955. The warmest low of the last 31 years was 73 in 1989. The record warmest low of 82 occurred back in 1916. 18 of the last 31 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 1977 the low was a cool 52. In 1972 the high was a cool 71. In 1964 the high was 89 with a low of 59, a 30 degree spread. In 1962 the low was a cool 51.

More recently, there was a small spread of six degrees in 1981 (69/63). The large spreads were 35 degrees in 1985 (87/52), 33 degrees in 1979 (89/56) and 33 degrees in 1988 (93/60).

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. 16 of the last 31 lows (52%) 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 began at 5:09 and sunrise was at 5:41. Sunset is at 20:18 and civil twilight ends at 20:50. Nautical twilight ends at 21:30 and astronomical twilight ends at 22:16. There's a total of 14 hours, 37 minutes of daylight today and 15 hours, 41 minutes between twilights. Tomorrow twilight begins at 5:10 and sunrise is at 5:42. The moon is waning gibbous and was full two nights ago at 20:27 (the full Buck or Thunder moon). Illumination was 99% at midnight, will be 97% at noon and 96% at midnight tonight. Moonset was at 7:16 this morning. Moonrise is at 20:56 tonight. Moonset is at 8:16 tomorrow morning. Moonlight time is 10 hours, 20 minutes which is 38 minutes longer than yesterday. -Bernie-