April 10: ORD

Today is April 10th. It's the 101st day of the year. 265 days remain. It's week 15 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. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. 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 57 and the normal low is 37. I've calculated the 33-year averages at 56 and 35.

On the warm side, last year, in 2011 (O'Hare's warmest April 10th) the high was 83 with the record warmest low of 56. The former record warmest low was 55 in 1945. In 2005 the high was 79 with a low of 44, a 35 degree spread. In 1981 the high was 69 with a low of 50. Six years later, in 1987, the high was 74 with a low of 45. The other warm highs were 74 two years ago (in 2010), 71 in 2006 and 69 in 1992. The record high of 90 was set back in 1930 at the University of Chicago. 23 of the past 33 highs (70%) were in the: 40s (11) and 50s (12). On the warm side, ten highs (30%) were in the: 60s (5) and 70s (4) and 80s (1). Our most recent 60s high was 64 in 2002. O'Hare's second warmest April 10th (in 1977) was also the year of its highest temperature of the date, that of 85 degrees. The low in 1977 was also a warm 50 degrees.

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1977 the high was 85 with a low of 50, a 35 degree spread and warm day. In 1976 the high was a warm 72 with a low of 37, a 35 degree spread. In 1975 the high was a cold 44 degrees. In 1973 the high was a cold 35 with a low of 28, a seven degree spread and cold day. In 1971 the high was a warm 69 with a low of 32, a 37 degree spread. In 1966 the low was a cold 24 degrees. In 1961 the high was a cold 45 degrees. In 1960 the low was a cold 24 degrees. In 1959 the high was a cold 38 with a low of 28, a cold day.

More recently, we had a small spread of seven degrees in 2000 (40/33). The large spreads were more numerous: 37 degrees in 2006 (71/34), 36 degrees two years ago, in 2010 (74/38), 32 degrees in 1996 (62/30), 32 degrees in 2003 (58/26), 31 degrees in 1986 (60/29) and 30 degrees in 2002 (64/34).

On the cold side, in 1989 (O'Hare's coldest April 10th) the high was 40 with the record low of 18. In 1997 the high was 40 with a low of 21. In 1980 the high was 40 with a low of 29. In 1982 the high was 43 with a low of 28. In 1979 the high was 45 with a low of 26. The other cold highs were 40 in 2000, 41 in 1995 and 44 in 1983. The record coldest high of 32 occurred way back in 1892, at a time when the official readings were taken adjacent to Lake Michigan. O'Hare's coldest high of 35 occurred in 1973. The other cold 30s high was 38 in 1959. 17 of the last 33 lows (52%) were in the 30s. Nine lows (27%) were in the cold: 10s (a.k.a. teens) (1) and 20s (8). Seven lows (21%) were in the warm: 40s (5) and 50s (2). Our most recent 40s low was 44 in 2005.

There was an instance of back-to-back-to-back years in which temperatures were just about as opposite as they can be. In 1980 the high was 40 with a low of 29, overall 12.5 degrees BELOW normal. Then in 1981 the high was 69 with a low of 50, overall 12.5 degrees ABOVE normal. In 1982 the high was 43 with a low of 28, overall 11.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:51 and sunrise is at 6:20. Sunset is at 19:30 and twilight ends at 19:59. There's a total of 13 hours, 10 minutes of daylight today and 14 hours, 8 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:49 and sunrise is at 6:18. The moon is waning gibbous. Illumination was 83% at midnight, will be 79% at noon and 74% at midnight tonight. Moonset is at 9:01 this morning. Moonrise is at 0:31 tomorrow morning. Moonset is at 10:03 tomorrow morning. Moonlight time is 9 hours, 1 minute which is 24 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. Earth Day is in 12 days.