March 25: ORD

Today is March 25th. It's the 85th day of the year. 281 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. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 50 and the normal low is 32. I've calculated the 33-year averages at 49 and 32.

On the warm side, in 2007 (O'Hare's warmest March 25th) the high was the record high of 79 with a low of 48, a 31 degree spread. The former record high of 75 was first set in 1939 and then tied 1967. In 1986 the high was 72 with a low of 51. In 2004 the high was 62 (our most recent 60s high) with the record warmest low of 57, a five degree spread. The record warmest low of 57 first occurred in 1945. In 1988 the high was 62 with a low of 44. In 2000 the high was 61 with a low of 44. The other warm highs were 65 in 1991 and 63 in 1989. 24 of the past 33 highs (73%) were in the: 30s (6), 40s (10) and 50s (8). On the warm side, seven highs (22%) were in the: 60s (5) and 70s (2). Prior to 1979, O'Hare's warmest highs were 75 in 1967 (which was the warmest until 2007), 67 in both 1968 and 1976, 65 in 1963 and 62 in 1977. On the cold side, two highs were in the 20s. Prior to 1979, the cold highs were 25 in 1960 and 26 in 1965.

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 32 with a low of 25, a seven degree spread and cold day. In 1977 the high was a warm 62 with a low of 30, a 32 degree spread. In 1976 the high was a warm 67 with a low of 34, a 33 degree spread. In 1975 the high was 32 with a low of 23, a cold day. In 1974 the high was 44 with a cold low of 10, a 34 degree spread and cold day. That low of 10 was colder than the record low of 12 at Midway the same year (1974). In 1973 the high was 47 with a low of 40, a seven degree spread. In 1971 the high was a cold 38 degrees. In 1969 the high was a cold 35 degrees. In 1968 the high was a warm 67 with a low of 38, a warm day. In 1967 the high was a warm 75 with a low of 41, a 34 degree spread and warm day. In 1966 the high was 37 with a low of 16, a cold day. In 1965 the high was 26 with a low of 17, another cold day. In 1964 the high was a cold 35 with a low of 22, yet another cold day. In 1963 the high was 65 with a low of 55, a warm day. In 1960 the high was 25 with a low of 9, a cold day. That low of 9 was another reading that was colder than the record of 12 set in 1974. In 1959 the high was 43 with a low of 36, a seven degree spread.

More recently, we had small spreads of six degrees in 2005 (39/33) and seven degrees in 1980 (35/28). There were large spreads of 40 degrees in 1996 (56/16), 33 degrees in 1995 (58/25), 32 degrees in 1981 (57/25) and 32 degrees in 1991 (65/33).

On the cold side, in 1979 the high was 25 with a low of 16. In 2001 the high was 25 with a low of 19, a six degree spread. In 1983 the high was 32 with a low of 20. In 2002 the high was 31 with a low of 24, a seven degree spread. Last year, in 2011, the high was 34 with a low of 24. The other cold low was 16 in 1996. The other cold highs were 35 in 1980 and 38 in 1999. The record low of 12 was originally set in 1940 and tied in 1974. The record coldest high of 19 was set way back in 1894, at a time when the official readings were taken adjacent to Lake Michigan. 23 of the last 33 lows (70%) were in the: 20s (12) and 30s (11). O'Hare recorded consecutive 20s & 30s lows as follows: six from 1980 through 1985 and seven from 1989 through 1995. Three lows (9%) were in the cold 10s (a.k.a. teens). O'Hare's coldest March 25th was in 1960 when the high was 25 with a low of 9, O'Hare's coldest low of the date. The second coldest low was 10 in 1974. Seven lows (21%) were in the warm: 40s (5) and 50s (2). O'Hare had a warm low of 55 in 1963 which was the warmest low until the current record warmest low of 57 occurred in 2004.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 2000 the high was 61 with a low of 44, overall 11.5 degrees ABOVE normal. Then in 2001 the high was 25 with a low of 19, overall 19 degrees BELOW normal.

Today is a major day in Chicago's snow history. At O'Hare in 1965, this was the sixth of seven days in which a total of 10.2 inches fell. Today 0.2 inches fell. In 1970 at O'Hare, this was the second of five days in which 11.8 inches fell. Today 5.8 inches fell. At Midway in 1970, 5.4 inches fell. This was the first of two days in which a total of 14.3 inches fell. In 1930 at the University of Chicago, a total of 21.6 inches fell on the 24th and 25th. 14.4 inches fell in an unspecified 24 hour time frame during these two days. Tom Skilling of WGN-TV said in his blog that the total was 19.2 inches. So there appears to be a slight discrepancy between the totals.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:19 and sunrise is at 6:47. Sunset is at 19:12 and twilight ends at 19:40. There's a total of 12 hours, 25 minutes of daylight today and 13 hours, 21 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:17 and sunrise is at 6:45. The moon is waxing crescent. Illumination was 6% at midnight, will be 9% at noon and 12% at midnight tonight. Moonrise is at 7:56 this morning. Moonset is at 22:32 tonight. Moonrise is at 8:30 tomorrow morning. Moonlight time is 14 hours, 36 minutes which is 27 minutes longer than yesterday.
 

Spring began on March 12th and runs for 84 days through June 3rd. Cool Spring began on March 12th and runs for 32 days through April 12th. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 60s and 70s usually occur infrequently. April Fools' Day and Palm Sunday are in seven days.