August 25: ORD

Today is August 25th. It's the 237th day of the year. 128 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 60. I've calculated the 31-year averages at 82 and 63.

On the hot side, in 2003 the high was the co-record high of 95 with a low of 71. In 1995 the high was 90 with our warmest low of 73. The other co-record high of 95 occurred in 1991. The record highs of 95 were originally set at Midway in 1953 and 1959. To round out the 90s highs, it hit 90 in 1994. Other warm 70s lows were 71 in 2003 and 70 in 1993. The record warmest low of 74 occurred in 1959. Over the last 31 years, 17 highs were 80s. Four highs were in the warmer 90s. Ten highs were in the cooler: 60s (1) and 70s (9).

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1977 the high was 79 with a cool low of 48, a 31 degree spread. That low of 48 was just above the record low. In 1975 the low was a warm 73. 1969 was the start of four consecutive days of highs of 86 degrees (from the 25th to the 28th). In 1967 the high was 82 with a low of 50, a 32 degree spread. In 1964 the low was a cool 47, equal to the record low. In 1959 the high was 94 with a low of 73, a hot day. This was a year of one of the co-record highs.

More recently, there were small spreads of six degrees in 1987 (62/56) and seven degrees in 1999 (73/66).

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. The coolest temperatures were 52 degrees. This happened in both 1979 and 1984. The record low of 47 was set in 1917. The coolest high was the record coolest high of 62, which occurred in 1987. The former record coolest high of 63 occurred in 1965. Over the last 31 years, 18 lows were in the 60s. Ten lows were in the cooler 50s. Three lows were in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:42 and sunrise is at 6:11. Sunset is at 19:39 and twilight ends at 20:08. There's a total of 13 hours, 28 minutes of daylight today and 14 hours, 26 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 5:43 and sunrise is at 6:12. The moon reached full yesterday as the full Sturgeon or Grain moon at 12:05, just after noon and is waning gibbous today. Illumination was 100% at midnight, will be 99% at noon and 98% at midnight tonight. Moonset was at 7:08 this morning and moonrise is at 19:45 tonight. Moonset is at 8:08 tomorrow morning. Moonlight time is 11 hours, 23 minutes which is 38 minutes longer than yesterday. -Bernie-