April 4: ORD

Today is April 4th. It's the 94th day of the year. 271 days remain. It's week 14 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 53 and the normal low is 34. I've calculated the 32-year averages at 52 and 34.

On the warm side, in 1997 the high was 75 with a low of 51. In 1988 the high was 68 with a low of 47. Last year, in 2010, the high was 76 with a low of 39, a 37 degree spread. In 1999 the high was 67 with a low of 44. Other warm highs were 68 in both 1981 and 2005. Another warm low was 48 in 1991. The record high of 79 and record warmest low of 60 were set on the same warm day back in 1929. The record high of 79 first occurred in 1921. 25 of the last 32 highs (78%) were in the: 40s (9), 50s (9) and 60s (7). On the warmer side, two highs were in the 70s. On the cold side, five highs were in the 30s.

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1975 the high was 36 with a low of 13, a cold day and year of the record low. In 1973 the high was a cold 39 with a low of 34, a five degree spread. In 1972 the high was 40 with a low of 22, a cold day. In 1964 the high was a cold 38 with a low of 25, a cold day.

More recently, we had a small spreads of seven degrees in: 1984 (44/37), 1996 (37/30) and 2003 (39/32). There were large spreads of 32 degrees in both 1981 (68/36) and 2005 (68/36). There was also a large spread of 31 degrees in 1987 (50/19).

On the cold side, in 1982 the high was 39 with a low of 20. Two decades later, in 2002, the high was 37 with a low of 25. In 1993 the high was 41 with a low of 21. In 2007 the high was 35 with a low of 28, a seven degree spread. Other cold lows were 19 in 1987 and 21 in 1995. Other cold highs were 37 in 1996 and 39 in 2003. The record low of 16 was set in 1975 and the record coldest high of 28 occurred way back in 1891. 17 of the last 32 lows (53%) were in the 30s. Nine lows (28%) were in the cold: 10s (a.k.a. teens) (1) and 20s (8). Six lows (19%) were in the warmer: 40s (5) and 50s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:03 and sunrise is at 6:31. Sunset is at 19:22 and twilight ends at 19:51. There's a total of 12 hours, 51 minutes of daylight today and 13 hours, 48 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:01 and sunrise is at 6:30. The moon is waxing crescent and reached new yesterday at 9:32. Illumination was 1% at midnight, will be 1% at noon and 3% at midnight tonight. Moonrise is at 6:36 this morning. Moonset is at 20:49 tonight. Moonrise is at 7:05 tomorrow morning. Moonlight time is 14 hours, 13 minutes which is 34 minutes longer than yesterday.

The warm part of Spring (Warm Spring) begins in nine days 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. Palm Sunday is in 13 days. -Bernie-