March 10: ORD

Today is March 10th. It's the 70th day of the year. 296 days remain. It's week 10 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 44 and the normal low is 27. I've calculated the 33-year averages at 42 and 24.

On the warm side, two years ago, in 2010, the high was 62 with a low of 46 (O'Hare's warmest low of the date). In 1990 the high was 62 with a low of 39. Five years before that, in 1985, the high was 64 with a low of 32, a 32 degree spread. The other warm highs were 61 three years ago in 2009, 58 in 1986 and 57 in 1997. The record high of 70 was set in 1955 at Midway. The record warmest low of 52 occurred way back in 1876, at a time when the official readings were taken adjacent to Lake Michigan. 21 of the past 33 highs (64%) were in the: 20s (6), 30s (10) and 40s (5). O'Hare's most recent 40s high was 49 in 2004. On the warm side, 12 highs (36%) were in the: 50s (8) and 60s (4). Tied with 2010 as O'Hare's warmest March 10th is 1977 with its high of 67 and low of 41. Tied with 1990 as O'Hare's second warmest March 10th is 1973 with its high of 62 and low of 39. The other pre-1979 warm highs are 60 in 1967 and 56 in 1966.

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1977 the high was 67 with a low of 41, a warm day. In 1974 the high was 42 with a low of 35, a seven degree spread. In 1973 the high was 62 with a low of 39, a warm day. In 1972 the low was a cold 15 degrees. In 1970 the high was a cold 31 degrees. In 1967 the high was a warm 60 with a low of 37, a warm day. In 1966 the high was 56 with a low of 39, a warm day. In 1965 the high was a cold 30 with a low of 18, a cold day. In 1962 the high was 36 with a low of 32, a four degree spread. In 1961 the low was a cold 15 degrees. In 1960 the high was a cold 30 degrees.

More recently, we had small spreads of five degrees last year, in 2011 (37/32) and six degrees in 1983 (30/24). There was another large spread of 32 degrees in 2001 (50/18).

On the cold side, in 2003 (O'Hare's coldest March 10th) the high was 20 (our most recent 20s high) with the record low of 2. The former record low of 5 occurred way back in 1892. In 1979 the high was 22 with a low of 9. Five years later, in 1984, the high was 28 with a low of 6. In 1998 the high was 23 with a low of 13. Six years earlier, in 1992, the high was 24 with a low of 15. A decade later, in 2002, the high was 28 with a low of 14 (our most recent 10s (a.k.a. teens) low. The other cold highs were 30 in both 1983 and 1987. The other cold low was 14 in 1996. The record coldest high of 18 occurred in 1948 at Midway. 24 of the last 33 lows (73%) were in the: 20s (12), 30s (11) and 40s (1). O'Hare's pre-1979 warm lows were 41 in 1977 and 39 (1966 & 1973). On the cold side, nine lows (27%) were in the: single digits (3) and 10s (a.k.a. teens) (6).

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1984 the high was 28 with a low of 6, overall 19 degrees BELOW normal. Then in 1985 the high was 64 with a low of 32, overall 12 degrees ABOVE normal.

Today is a major day in Chicago's snow history. In 1999, 1.0 inches fell. This was the sixth of six days in which a total of 18.2 inches fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:45 and sunrise is at 6:13. Sunset is at 17:55 and twilight ends at 18:23. There's a total of 11 hours, 42 minutes of daylight today and 12 hours, 38 minutes between twilights. We gained four minutes of daylight from yesterday. Tomorrow twilight begins at 6:43 and sunrise is at 7:11. The moon is waning gibbous, having reached the full Worm (a.k.a. Sap) moon two days ago at 3:39. Illumination was 95% at midnight, will be 92% at noon and 89% at midnight tonight. Moonset is at 7:04 this morning. Moonrise is at 21:12 tonight. Moonset is at 8:42 tomorrow morning. Moonlight time is 9 hours, 52 minutes which is 42 minutes shorter than yesterday.

Winter began December 1st and runs for 102 days through March 11th. High temperatures in this period are usually in the 20s and 30s. Highs in the 40s and 50s occur infrequently. St. Patrick's Day is in seven days.