April 6: ORD

Today is April 6th. It's the 96th day of the year. 269 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 54 and the normal low is 34. I've calculated the 32-year averages at 55 and 34.

On the warm side, in 1991 the high was 83 with a low of 58. In 2005, the high was 80 with a low of 45, a 35 degree spread. Last year, in 2010, the high was 76 with a low of 47. In 2004 the high was 72 with a low of 39, a 33 degree spread. Other warm highs were 67 in 1995, 66 in 1980 and 66 in 1992. The record high of 84 and record warmest low of 69 were set on the same warm day back in 1929. 18 of the last 32 highs (56%) were in the: 50s (8) and 60s (10). On the warmer side, four highs (13%) were in the: 70s (2) and 80s (2). On the cold side, ten highs (31%) were in the: 30s (6) and 40s (4).

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 a cold 38 degrees. In 1973 the high was a warm 67 degrees. In 1972 the high was 65 with a low of 33, a 32 degree spread. In 1967 the high was 49 with a low of 42, a seven degree spread. In 1966 the high was a cold 40 with a low of 35, a five degree spread. In 1965 the high was a warm 71 with a low of 42, a warm day. In 1964 the high was a warm 70 with a low of 45, another warm day. In 1963 the high was a warm 72 with a low of 37, a 35 degree spread. In 1961 the high was 43 with a low of 36, a seven degree spread.

More recently, we had a small spread of seven degrees in 2003 (37/30). There were large spreads of 34 degrees in 1981 (56/22), 33 degrees in 1992 (66/33) and 31 degrees in 1995 (67/36).

On the cold side, in 1982 the high was the record coldest high of 32 with the record low of 15. Three years earlier, in 1979, the high was 36 with a low of 19. In 2007 the high was 36 with a low of 23. In 1994 the high was 36 with a low of 26. Four years before, in 1990, the high was 38 with a low of 24. In 1996 the high was 40 with a low of 25. Another cold low was 22 in 1981. Another cold high was 37 in 2003 and 40 two years ago in 2009. 14 of the last 31 lows (44%) were in the 30s. Nine lows (28%) were in the cold: 10s (a.k.a. teens) (2) and 20s (7). Nine lows (28%) were in the warmer: 40s (8) and 50s (1).

1982 and 1979 had some very cold low temperatures. In 1982, lows were: Rockford: 11, Barrington: 13, Chicago Botanical Gardens: 17, University of Chicago: 18, Midway: 16, Elgin: 12, Marengo: 11 and Wheaton: 14. In 1979, lows were: Midway: 16, Barrington: 18, Elgin: 15, Marengo: 18, Rockford: 13, DeKalb: 23, Wheaton: 18 and Aurora: 19.

Today is a major day in Chicago's snow history. In 1982, Midway had 0.7 inches, the final part of a total of 10.5 inches. In 1938, the city recorded nine (9.0") inches of snow.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:59 and sunrise is at 6:28. Sunset is at 19:24 and twilight ends at 19:53. There's a total of 12 hours, 56 minutes of daylight today and 13 hours, 54 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:58 and sunrise is at 6:26. The moon is waxing crescent and reached new three days ago at 9:32. Illumination was 6% at midnight, will be 9% at noon and 12% at midnight tonight. Moonrise is at 7:38 this morning. Moonset is at 22:50 tonight. Moonrise is at 8:18 tomorrow morning. Moonlight time is 15 hours, 12 minutes which is 27 minutes longer than yesterday.

The warm part of Spring (Warm Spring) begins in seven 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 11 days. -Bernie-