April 16: ORD

Today is April 16th. It's the 107th day of the year. 259 days remain. It's week 16 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 59 and the normal low is 39. I've calculated the 33-year averages at 59 and 39.

On the warm side, in 2002 (O'Hare's warmest April 16th) the high was the record high of 87 with the near-record warmest low of 68. The former record high of 86 occurred in 1976 and the current record warmest low of 69 also occurred in 1976, both at Midway. In 2004 the high was 82 with a low of 58. In 1982 the high was 68 with a low of 58. The other warm highs were 74 in 2005, 73 in 1989 and 73 in 2008. 14 of the past 33 highs (43%) were in the 60s. On the warm side, five highs (15%) were in the: 70s (3) and 80s (2). O'Hare's second warmest April 16th was in 1976 (high of 85, low of 68). The lows of 68 in 1976 and 2002 were O'Hare's warmest lows of the date and only lows in the 60s for the date. Some of O'Hare's other pre-1979 warm highs were 84 in 1964, 83 in 1977, 78 in 1963 and 77 in 1969. On the cold side, 14 highs (42%) were in the: 40s (10) and 50s (4). O'Hare recorded six consecutive 40s & 50s highs from 1996 through 2001. Our most recent 50s high was 51 in 1997. 

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1978 the high was a cold 46 degrees. In 1977 the high was 83 with a low of 55, a warm day. In 1976 the high was 85 with a low of 68, a warm day and year of the record warmest low of 69 at Midway. In 1970 the high was 72 with a low of 52, a warm day. In 1969 the high was a warm 77 with a low of 49, a warm day. In 1967 the high was 74 with a low of 54, a warm day. In 1966 the high was 62 with a cold low of 27, a 35 degree spread. In 1964 the high was 84 with a low of 51, a 33 degree spread and warm day. In 1963 the high was 78 with a low of 53, a warm day. In 1962 the high was 48 with a cold low of 24, a cold day. In 1961 the high was a cold 33 with a low of 28, a five degree spread and cold day. In 1960 the high was 72 with a low of 51, a warm day. In 1959 the high was a warm 74 degrees.

More recently, we had a small spread of four degrees in 1999 (46/42). There were large spreads of 37 degrees in 2005 (74/37), 31 degrees in 1989 (73/42) and 30 degrees in 2007 (62/32).

On the cold side, in 1983 the high was 43 with a low of 26. In 2001 the high was 42 with a low of 29. In 1980 the high was 49 with a low of 24. The other cold highs were 43 in 1984, 43 in 1993, 45 in 1986 and 46 in 1999. The record low of 18 and record coldest high of 27 were set on the same cold day way back in 1875, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 30s (17) and 40s (10). Three lows were in the cold 20s. O'Hare's coldest April 16th was in 1961 as the high was 33 (O'Hare's only 30s high of the date) with a low of 28, a small five degree spread. Keep in mind that it was snowing today in 1961. In 1962 the low was 24 degrees. The lows of 24 in 1962 and 1980 are O'Hare's coldest readings of the date. Three lows were in the warm: 50s (2) and 60s (1).

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In 1982 the high was 68 with a low of 58, overall 14 degrees ABOVE normal. Then in 1983 the high was 43 with a low of 26, overall 14.5 degrees BELOW normal. In the second instance, in 2001 the high was 42 with a low of 29, overall 13.5 degrees BELOW normal. Then in 2002 the high was 87 with a low of 68, overall 28.5 degrees ABOVE normal.

Today is a major day in Chicago's snow history. 1961 was the year. O'Hare had 4.7 inches, the second of two days of 5.9 inches of snow. Midway had 5.4 inches, the second of three days of 6.8 inches of snow. Rockford recorded 4.4 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:41 and sunrise is at 6:10. Sunset is at 19:36 and twilight ends at 20:06. There's a total of 13 hours, 26 minutes of daylight today and 14 hours, 25 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:39 and sunrise is at 6:09. The moon is waning crescent. Illumination was 23% at midnight, will be 19% at noon and 15% at midnight tonight. Moonrise was at 3:44 this morning. Moonset was at 15:27 this afternoon. Moonrise is at 4:10 tomorrow morning. Moonlight time is 11 hours, 43 minutes which is 33 minutes longer than yesterday. 

Spring began on March 12th and runs for 84 days through June 3rd. Warm Spring began on April 13th and runs for 52 days through June 3rd. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 80s and 90s occur infrequently. Earth Day is in six days. Arbor Day is in 11 days.