April 12: ORD

Today is April 12th. It's the 103rd day of the year. 263 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 58 and the normal low is 38. I've calculated the 33-year averages at 55 and 38.

On the warm side, in 2006 the high was 76 with a low of 58 (O'Hare's warmest low of the date). In 1998 the high was 73 with a low of 55. In 1979 the high was 77 with a low of 45, a 32 degree spread. In 1985 the high was 76 with a low of 43, a 33 degree spread. The other warm high was 70 two years ago, in 2010. The record high of 86 was originally set in 1971 and tied in 1977, both at Midway. The record warmest low of 60 occurred in 1896, at a time when the official readings were taken adjacent to Lake Michigan. 22 of the past 33 highs (67%) were in the: 40s (9) and 50s (13). O'Hare recorded ten consecutive 40s & 50s highs from 1986 through 1995. On the warm side, nine highs (27%) were in the: 60s (4) and 70s (5). Our most recent 60s high was 67 in 2002. O'Hare's warmest April 12th was in 1977 as the high was 83 with a low of 57. O'Hare's warmest temperature of the date was 85 in 1971. O'Hare's other pre-1979 warm highs were 81 in 1968, 73 in 1974 and 72 in 1960. On the cold side, two highs (6%) 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 83 with a low of 57, a warm day and year of the record high of 86 at Midway. In 1976 the low was a cold 25 degrees. In 1974 the high was 73 with a low of 53, a warm day. In 1971 the high was a warm 85 with a low of 45, a 40 degree spread and warm day. 1971 is also the original year of the record high of 86 at Midway. In 1968 the high was 81 with a low of 54, a warm day. In 1964 the low was a warm 51 degrees. In 1963 the high was 61 with a cold low of 26, a 35 degree spread. In 1962 the high was a cold 45 degrees. In 1961 the high was a cold 44 with a low of 37, a seven degree spread. In 1960 the high was a warm 72 with a low of 42, a 30 degree spread.

More recently, we had an additional small spread of seven degrees in 1981 (50/43).


On the cold side, in 1997 (O'Hare's coldest April 12th) the high was 36 with a low of 30, a six degree spread. In 1990 the high was 45 with a low of 25 (O'Hare's co-coldest low of the date (the low was also 25 in 1976)). In 2007 the high was 38 with a low of 33. The 30s highs just mentioned were the only 30s highs in O'Hare's history for the date. Three years earlier, in 2004, the high was 42 with a low of 30. The other cold highs were 41 in 1992, 42 in 2008 and 44 in 1995. The record low of 21 was originally set back in 1939 at the University of Chicago and tied in 1957 at Midway. The record coldest high of 34 occurred in 1950 at Midway. 27 of the last 33 lows (82%) were in the: 30s (16) and 40s (11). Four lows were in the cold 20s. O'Hare's second coldest low of the date was 26 in 1963. Two lows since 1979 were in the warm 50s.

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In 1997 the high was 36 with a low of 30, overall 15 degrees BELOW normal. Then in 1998 the high was 73 with a low of 55, overall 16 degrees ABOVE normal. In the second instance, in 2006 the high was 76 with a low of 58, overall 19 degrees ABOVE normal. Then in 2007 the high was 38 with a low of 33, overall 12.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:48 and sunrise is at 6:17. Sunset is at 19:32 and twilight ends at 20:01. There's a total of 13 hours, 15 minutes of daylight today and 14 hours, 13 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:46 and sunrise is at 6:15. The moon is waning gibbous. Illumination was 63% at midnight, will be 58% at noon and 52% at midnight tonight. Moonrise was at 1:23 this morning. Moonset was at 11:09 this morning. Moonrise is at 2:07 tomorrow morning. Moonlight time is 9 hours, 46 minutes which is 14 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 (today). 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 ten days.