July 20: ORD

Today is July 20th. It's the 201st day of the year. 164 days remain. It's week 29 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 85 and 65.

On the hot side, there were no days of a mean of 11.5 degrees or more above normal. The record high of 101 was set in 1980. In 1980 the low was 69, so the spread on that day was 32 degrees. Other hot highs were 96 in both 1987 and 1991. The warmest low was 74 in 1991. The record warmest low of 79 occurred in 1977. 13 of the last 31 highs were 80s. Nine highs were in the warmer: 90s (8) and 100s (1). Nine highs were in the cooler 70s, including two of the last three. Through 2010, this is the average tenth hottest day of the year.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1977 the high was 95 with a warm low of 76, a hot day and year of the record warmest low. In 1972 the low was a warm 77. In 1970 the high was a cool 72. 1970 was the year of the record low. The low was 55 at O'Hare and cooler at Midway (53 degrees). In 1966 the low was a cool 51.

More recently, there were no other large spreads of at least 30 degrees or no small spreads of up to seven degrees.

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. The lowest temperature was 54 in 1979. Last year's low was just a degree above at 55 degrees. The record low of 53 was set in 1970. The coolest highs were 71 in 1996 and 72 in 1989. The record coolest high of 65 occurred in 1950. 18 of the last 30 lows were 60s. Seven 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 5:02 and sunrise was at 5:35. Sunset is at 20:24 and twilight ends at 20:57. There's a total of 14 hours, 49 minutes of daylight today and 15 hours, 55 minutes between twilights. Tomorrow twilight begins at 5:03 and sunrise is at 5:36. The moon is waxing gibbous. Illumination was 69% at midnight, will be 74% at noon and 79% at midnight tonight. Moonset was at 42 minutes past midnight. Moonrise is at 16:14. Moonset is at 1:25 tomorrow morning. Moonlight time is 8 hours, 28 minutes which is 29 minutes shorter than yesterday.

Parent's Day is in five days. - Bernie -