April 21: ORD

Today is April 21st. It's the 111th day of the year. 254 days remain. It's week 16 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 60 and the normal low is 39. I've calculated the 32-year averages at 60 and 40.

On the warm side, in 1985 the high was the record high of 88 with the record warmest low of 63. In 2001 the high was 82 with a low of 55. In 1980 the high was 79 with a low of 46, a 33 degree spread. Other warm highs were 77 in 2007, 75 in 2008 and 72 in 1987. 21 of the last 32 highs (66%) were in the: 50s (13) and 60s (8). On the warmer side, seven highs (22%) were in the: 70s (5) and 80s (2). On the cold side, four highs (12%) were in the 40s.

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1976 the low was a warm 52 degrees. In 1974 the high was 70 with a warm low of 61, a warm day. In 1973 the high was 68 with a warm low of 59, a warm day. In 1972 the high was a cold 47 with a low of 41, a six degree spread. In 1968 the low was a warm 53 degrees. In 1967 the high was 72 with a low of 51, a warm day. In 1964 the high was a warm 72 degrees. In 1962 the high was a warm 80 with a low of 44, a warm day. In 1960 the high was 73 with a low of 55, a warm day. In 1959 the high was a cold 47 with a low of 29, a cold day.

More recently, we had small spreads of three degrees in 2002 (42/39), six degrees in 1998 (53/47) and seven degrees two years ago in 2009 (44/37). The large spreads were: 34 degrees in 2007 (77/43), 33 degrees in 2008 (75/42) and 32 degrees in 1987 (72/40).

On the cold side, in 1986 the high was 45 with the record low of 27. Two years later, in 1988, the high was 45 with a low of 29. Other cold highs were 42 in 2002 and 44 two years ago in 2009. The record coldest high of 35 was set back in 1936. 18 of the last 32 lows (56%) were in the 40s. In fact, 7 of the last 8 lows were in the 40s. 12 lows (38%) were in the cold: 20s (4) and 30s (8). Two lows (6%) were in the warmer: 50s (1) and 60s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:34 and sunrise is at 6:04. Sunset is at 19:41 and twilight ends at 20:11. There's a total of 13 hours, 37 minutes of daylight today and 14 hours, 37 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:32 and sunrise is at 6:02. The moon is waning gibbous. Illumination was 87% at midnight, will be 83% at noon and 78% at midnight tonight. Moonset is at 8:30 this morning. Moonrise is at 0:13 tomorrow morning. Moonset is at 9:32 tomorrow morning. Moonlight time is 8 hours, 30 minutes which is 12 minutes longer than yesterday.

The warm part of Spring (Warm Spring) began on April 13. Warm Spring runs for 52 days, through June 3. High temperatures in this period are usually in the 50s, 60s and 70s. Warmer 80s and 90s occur infrequently. Good Friday and Earth Day are tomorrow. -Bernie-