March 20: ORD

Today is March 20th. It's the 79th day of the year. 286 days remain. It's week 12 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 48 and the normal low is 30. I've calculated the 31-year averages at 47 and 30.

On the warm side, in 2003 the high was 65 with a low of 43. Other warm highs were 62 in 2004, 61 (1991, 1994) and 60 in 1995. Another warm low was 43 in 2000. The record high of 76 was set back in 1921 and the record warmest low of 53 was set back in 1918. Unusual for just three years of separation for these records. 12 of the last 31 highs were 40s. On the warmer side, 11 highs were: 50s (6) and 60s (5). On the colder side, eight highs were: 30s (7) and 20s (1). Today is the midrange (average of earliest and latest dates) date of our first high in the 70s, based upon the last 32 years.

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1976 the high was 70 with a low of 47, a warm day. In 1975 the high was a warm high of 60. In 1972 the high was a warm 69 with a low of 38, a 31 degree spread and warm day. In 1970 the high was 41 with a low of 36, a five degree spread. In 1967 the high was 36 with a low of 33, a three degree spread. In 1966 the high was 56 with a low of 26, a 30 degree spread. In 1965 the high was 22 with a low of 0, a cold day. In 1960 the high was a cold 34 with a low of 20, a cold day.

More recently, we had small spreads of three degrees in 1998 (36/33), five degrees in 1983 (32/27) and seven degrees in 1993 (38/31). There was a large spread of 30 degrees in 2004 as the high was 62 with a low of 32.

On the cold side, in 1986 the high was 26 with a low of 8. Other cold highs were 32 in 1983, 36 half a decade later in 1988 and 36 a decade after that in 1998. The record low of 4 and record coldest high of 15 were set on the same day way back in 1885. 27 of the last 31 lows were: 20s (15) and 30s (12). One low was in the colder single digits. Three lows were in the warmer 40s. No lows have been in the 10s (a.k.a. teens) over the last 30 years.

Today is a major day in Chicago's snow history. At O'Hare in 1965, this was the first of seven days in which a total of 10.2 inches fell. Today just a tenth of an inch fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 6:29 and sunrise was at 6:57. Sunset is at 19:06 and twilight ends at 19:34. There's a total of 12 hours, 9 minutes of daylight today and 13 hours, 5 minutes between twilights. Tomorrow twilight begins at 6:27 and sunrise is at 6:55. The moon is waxing crescent. Illumination was 18% at midnight, will be 23% at noon and 27% at midnight tonight. Moonrise was at 8:56 this morning. Moonset is at 0:34 tomorrow. Moonrise is at 9:41 tomorrow. Moonlight time is 15 hours, 4 minutes which is 5 minutes shorter than yesterday.