April 29: ORD

Today is April 29th. It's the 119th day of the year. 246 days remain. It's week 17 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.

According to the National Climatic Data Center (NCDC), the normal high is 63 and the normal low is 42. I've calculated the 32-year averages at 64 and 43.

On the warm side, in 2004 the high was 78 with a low of 59. In 1987 the high was 83 with a low of 45, a 38 degree spread. Other warm highs were 82 in 2007, 79 last year (in 2010) and 75 in 2001. Another warm low was 54 in 1991. The record-tying high of 88 and record warmest low of 68 were set on the same day at Midway in 1970. The co-record high of 88 occurred way back in 1899. 27 of the last 32 highs (84%) were in the: 50s (8), 60s (11) and 70s (8). On the warmer side, two highs were in the 80s. On the cold side, three highs were in the 40s. We've seen all five categories of high temperatures in the past five years: 44 in 2008, 55 in 2009, 61 in 2006, 79 in 2010 and 82 in 2007.

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 70 with a low of 40, a 30 degree spread. In 1977 the high was 64 with a cold low of 30, a 34 degree spread. That low of 30 was lower than the record low. In 1975 the high was a warm 76 with a low of 39, a 37 degree spread. In 1974 the high was 69 with a warm low of 60, a warm day. In 1971 the high was a cold 51degrees. In 1970 the high was 86 with a low of 69, a hot day (the day of the records). In 1969 the high was a cold 51 degrees. In 1966 the high was 67 with a low of 36, a 31 degree spread. In 1965 the high was 70 with a low of 35, a 35 degree spread. In 1961 the low was a cold 30 degrees (lower than the record low).

More recently, we had large spreads of 37 degrees in 2007 (82/45), 33 degrees in 1985 (69/36), 33 degrees last year (in 2010) (79/46), 32 degrees in 1988 (65/33) and 31 degrees in 1986 (74/43).

On the cold side, three years ago (in 2008) the high was 44 with a record-tying low of 31. In 1996 the high was 45 with a low of 36. Another cold high was 48 in 1979. The co-record low of 31 occurred in 1958. O'Hare had lows of 30 degrees in both 1977 and 1961 but in these years O'Hare was not the official station of record for Chicago. The record coldest high of 39 was set way back in 1893. 21 of the last 32 lows (66%) were in the 40s. Eight low were in the cold 30s. Three lows were in the warmer 50s. Yesterday, April 28, 2011, was the second coldest April 28 as the high was 45 with a low of 40, mean of 42.5. Only 2008 was colder (46/35). Yesterday was also only half a degree colder than three other days that had means of 43 degrees: 1979 (50/36), 1994 (51/35) and 1996 (50/36).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 5:22 and sunrise is at 5:52. Sunset is at 19:50 and twilight ends at 20:21. There's a total of 13 hours, 58 minutes of daylight today and 14 hours, 59 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:20 and sunrise is at 5:51. The moon is waning crescent. Illumination was 14% at midnight, will be 11% at noon and 8% at midnight tonight. Moonrise is at 3:51 this morning. Moonset is at 16:42 this afternoon. Moonrise is at 4:14 tomorrow morning. Moonlight time is 12 hours, 51 minutes which is 36 minutes longer than yesterday.

The warm part of Spring (Warm Spring) began on April 13. Warm Spring runs for 52 days, through June 3. High temperatures in this period are usually in the 50s, 60s and 70s. Warmer 80s and 90s occur infrequently. Arbor Day is today. National Teacher Day is in four days. Mother's Day is in nine days. -Bernie-