March 31: ORD

Today is March 31st. It's the 90th day of the year. 275 days remain. It's week 13 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 52 and the normal low is 33. I've calculated the 32-year averages at 55 and 35.

On the warm side, in 1986 the high was 83 with a low of 48, a 35 degree spread. Five years earlier, in 1981, the high was the record high of 87 with a low of 41, a 46 degree spread. Last year, in 2010, the high was 77 with a low of 51. In 1999 the high was 71 with a low of 48. A year earlier, in 1998, the high was 72 with a low of 45. In 2006 the high was 68 with a low of 45. Other warm lows were 46 in 1982 and 45 in 2007. The record warmest low of 60 was set in 1967. 21 of the last 32 highs (66%) were in the: 40s (11) and 50s (10). Our most recent 40s high was 48 in 2004. On the warmer side, ten highs (31%) were in the: 60s (5), 70s (3) and 80s (2). 4 of the last 5 years featured a warmer side high. On the cold side, one high was in the 30s.

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1978 the high was a warm 78 with a low of 39, a 39 degree spread and warm day. In 1975 the high was 58 with a low of 24, a 34 degree spread. In 1971 the high was a warm 74 with a low of 42, a 32 degree spread and warm day. In 1969 the high was 33 with a low of 12, a cold day. 1969 was also the year of the record low (12 at Midway). In 1968 the high was a warm 65 degrees. In 1967 the high was 68 with a low of 58, another warm day and year of the record warmest low. In 1966 the high was 54 with a low of 22, a 32 degree spread. In 1964 the high was 35 with a low of 19, a cold day. In 1963 the low was a warm 46 degrees. In 1960 the high was was a cold 38 with a low of 31, a seven degree spread.

More recently, we had a small spread of seven degrees in 1990 (45/38). There were large spreads of 31 degrees in 2003 (55/24) and 37 degrees in 2000 (63/26).

On the cold side, in 1987 the high was 40 with a low of 20. Two years later, in 1989, the high was 37 with a low of 33, a four degree spread. The record low of 12 originally occurred in 1923 and was tied in 1969. The record coldest high of 21 occurred in 1923. As you can see, 1923 was the coldest March 31. 17 of the last 32 lows (53%) were in the 30s. Seven lows (22%) were in the cold 20s. Eight lows (25%) were in the warmer: 40s (7) and 50s (1). The only 50s low of 51 occurred last year in 2010. This was only the second 50s low in O'Hare's history (see '1967' above) for the date.

Today is a major day in Chicago's snow history. Today and yesterday, back in 1926 at the University of Chicago, 8.7 inches fell. Rockford today had 13.5 of it's 16 inch total back in 1926.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:10 and sunrise is at 6:38. Sunset is at 19:18 and twilight ends at 19:46. There's a total of 12 hours, 40 minutes of daylight today and 13 hours, 36 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:08 and sunrise is at 6:36. The moon is waning crescent and will be new in three days at 9:32. Illumination was 10% at midnight, will be 7% at noon and 5% at midnight tonight. Moonrise is at 5:02 this morning. Moonset is at 16:51 this afternoon. Moonrise is at 5:24 tomorrow morning. Moonlight time is 11 hours, 49 minutes which is 35 minutes longer than yesterday.

April Fool's Day is tomorrow. The warm part of Spring (Warm Spring) begins in 13 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. -Bernie-