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 81 and the normal low is 62. I've calculated the 32-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 four years earlier in 1991 with a low of 66. The record highs of 95 were originally set at Midway in 1953 and 1959. The only other 90s high over the last 32 years was 90 in 1994. The only other 70s low was 70 in 1993. The record warmest low of 74 occurred in 1959. Since 1959 has both a co-record high and record warmest low, it is the hottest August 25th. 27 of the past 32 highs (84%) were in the: 70s (10) and 80s (17). Four highs were in the hot 90s. One high (62 in 1987) was in the cool 60s.

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 cold low of 48, a 31 degree spread. That low of 48 was just above the record low. 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 cool low of 50, a 32 degree spread. In 1964 the low was a cold 47 degrees which equals the record low. In 1960 today and tomorrow (the 25th & 26th), we had lots of sixes, sevens and eights. On the 25th, it was 86 and 68. On the 26th, it was 88 and 66. In both cases, the means were 77 degrees! In 1959 the high was a hot 94 with a low of 73, a hot day. 1959 is the year of one of the co-record highs and is the year of the record warmest low.

More recently, there was a small spread of seven degrees in 1999 (high of 73, low of 66).

On the cool side, in 1987 the high was the record coolest high of 62 with a low of 56. The former record coolest high of 63 occurred in 1965. In 1985 the high was 73 with a low of 56. Three years before, in 1982, the high was 75 with a low of 54. In 1997 the high was 72 with a low of 58. The coolest lows were 52 degrees. These occurred in 1979 and 1984. The record low of 47 was set back in 1917. 19 of the last 32 lows (59%) were in the 60s. Ten lows (31%) were in the cool 50s. Three lows (10%) were in the warm 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 lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:43 and sunrise is at 6:12. The moon is waning crescent and three days from new. Illumination was 19% at midnight, will be 15% at noon and 11% at midnight tonight. Moonrise is at 2:07 this morning. Moonset is at 17:16 this afternoon. Moonrise is at 3:15 tomorrow morning. Moonlight time is 15 hours, 9 minutes which is 19 minutes shorter than yesterday.

Summer began June 4 and runs for 110 days through September 21. High temperatures in this period are usually in the 70s and 80s. Highs in the 60s, 90s and 100s occur infrequently. Labor Day is in 11 days. 9/11 Remembrance Day and Grandparents Day are in 16 days.