August 24: ORD

Today is August 24rd. It's the 236th day of the year. 129 days remain. It's week 34 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 80 and the normal low is 61. I've calculated the 31-year averages at 81 and 62.

On the hot side, there were no days of a mean of at least 11.5 degrees above normal. The warmest (and only 90s high) was 90 in 1983. The record high of 100 was set in 1947. There were no 70s lows. A low of 69 occurred three times (1992, 1994 and 2007). The record warmest low of 78 occurred in 1975. Over the last 31 years, 30 highs (97%) were: 70s (12) and 80s (18). One high was in the warmer 90s.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1975 the high was 91 with a warm low of 79, a hot day and year of the record warmest low. In 1971 the high was 90 with a low of 59, a 31 degree spread. In 1969 the high was 87 with a low of 57, a 30 degree spread. In 1967 the low was a cool 48, equal to the record low. In 1966 the low was a cool 49, just above the record low. In 1965 the high was 82 with a cool low of 45, a 37 degree spread. That low of 45 is cooler than the record low. In 1964 the high was 78 with a cool low of 45, a 33 degree spread. That low of 45 was also cooler than the record low. In 1963 the high was 70 with a low of 66, a four degree spread. In 1962 the high was a hot 94 with a low of 71, a hot day. In 1959 the high was a hot 92 with a low of 71, a hot day.

More recently, there was a large spread of 31 degrees in 1983 (90/59). There were small spreads of six degrees in 1989 (73/67) and seven degrees in 1999 (74/67).

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. The coolest day was in 1987 when we had our coolest high of 72 with our co-coolest low of 51. A low of 51 also occurred three years earlier in 1984. The record low of 48 was set in 1942. The record coolest high of 63 occurred way back in 1891. The official thermometer was located near Lake Michigan at the time. Over the last 31 years, 19 lows (61%) were in the 60s. 12 lows (39%) were in the cooler 50s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:41 and sunrise is at 6:10. Sunset is at 19:40 and twilight ends at 20:10. There's a total of 13 hours, 30 minutes of daylight today and 14 hours, 29 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 5:42 and sunrise is at 6:11. The moon reaches full today as the full Sturgeon or Grain moon at 12:05, just after noon. Illumination was 100% at midnight, will be 100% at noon and 100% at midnight tonight. Moonset is at 6:09 this morning and moonrise is at 19:24 tonight. Moonset is at 7:08 tomorrow morning. Moonlight time is 10 hours, 45 minutes which is 38 minutes longer than yesterday. -Bernie-