April 8: ORD

Today is April 8th. It's the 99th day of the year. 267 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. 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 56 and the normal low is 36. I've calculated the 33-year averages at 52 and 35.

On the warm side, in 1991 (tied with 1969 as O'Hare's warmest April 8th) the high was 74 with a low of 50. A decade later, in 2001, the high was 77 with a low of 45, a 32 degree spread. The other warm high was 68 in 1981. The other warm low was the record warmest low of 52 in 1993. The former record warmest low of 51 occurred way back in 1875. The record high of 80 was set back in 1931. The official readings in 1875 and 1931 were taken adjacent to Lake Michigan. 21 of the past 33 highs (64%) were in the: 40s (12) and 50s (9). O'Hare recorded six consecutive 40s & 50s highs from 2006 through 2011 (ongoing). On the warm side, nine highs (27%) were in the: 60s (7) and 70s (2). O'Hare's warmest high of the date was in 1969 (78 degrees) with a low of 46. 1969 is tied with 1991 as O'Hare's warmest April 8th. O'Hare's other pre-1979 warm highs occurred in the years after 1969: 72 in 1970 and 77 in 1971. On the cold side, three highs (9%) were in the 30s. 

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 a cold 41 degrees. In 1975 the high was a cold 44 degrees. In 1974 the high was a cold 39 degrees. In 1973 the high was a cold 43 with a low of 36, a seven degree spread. In 1972 the high was 35 with a low of 14, a cold day and year of the record low (see below). That low of 14 was colder than the official record low. In 1971 the high was a warm 77 with a low of 41, a 36 degree spread and warm day. In 1970 the high was a warm 72 with a low of 45, a warm day. In 1969 the high was a warm 78 with a low of 46, a 32 degree spread and warm day. In 1965 the high was 46 with a low of 39, a seven degree spread. In 1964 the high was a cold 40 with a low of 28, a cold day. In 1961 the high was 42 with a low of 21, a cold day. In 1960 the high was a cold 41 with a low of 28, a cold day.

More recently, we had small spreads of five degrees three years ago in 2008 (45/40), six degrees in 2002 (52/46) and seven degrees in 1993 (59/52). The large spreads were 30 degrees in both 1988 (66/36) and 1990 (61/31).

On the cold side, in 1997 the high was 33 with a low of 24. The year earlier, in 1996, the high was 40 with a low of 21. In 1982 the high was 35 with a low of 26. In 2003 the high was the record coldest high of 32 with a low of 31, a single degree spread. The record coldest high of 32 first occurred in 1914. In 1985 the high was 40 with a low of 25. In 2007 the high was 40 with a low of 28. In 2000 the high was 41 with a low of 27. In 2006 the high was 43 with a low of 26. The other cold high was 40 two years ago, in 2010. The record low of 20 was set in 1972 at Midway. 1972 was also the coldest April 8th at O'Hare as the high was 35 with a low of 14 (the coldest low of the date). The other pre-1979 30s high was 39 in 1974. There were five highs from 40 to 43 degrees (considered as cold) from 1960 to 1977. The coldest 20s low, pre-1979, was 21 in 1961. 31 of the last 33 lows (94%) were in the: 20s (11), 30s (12) and 40s (8). Two lows were in the warm 50s.

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 41 with a low of 27, overall 12 degrees BELOW normal. Then in 2001 the high was 77 with a low of 45, overall 15 degrees ABOVE normal.

Today is a major day in Chicago's snow history. In 1938, the city recorded 4.5 inches of snow. This was the last day of snow for April 1938, giving the month a total of 13.6 inches, the snowiest April in Chicago's history.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:55 and sunrise is at 6:23. Sunset is at 19:28 and twilight ends at 19:56. There's a total of 13 hours, 5 minutes of daylight today and 14 hours, 1 minute between twilights. We gained four minutes of daylight from yesterday. Tomorrow twilight begins at 5:53 and sunrise is at 6:22. The moon is waning gibbous, having reached the full Pink (a.k.a. Sprouting Grass/Egg/Fish) moon two days ago at 14:19. Illumination was 97% at midnight, will be 94% at noon and 91% at midnight tonight. Moonset is at 7:17 this morning. Moonrise is at 22:18 tonight. Moonset is at 8:05 tomorrow morning. Moonlight time is 8 hours, 59 minutes which is 33 minutes shorter 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. Easter is today. Earth Day is in 14 days.