May 4: ORD

Today is May 4th. It's the 124th day of the year. 241 days remain. It's week 18 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 66 and the normal low is 43. I've calculated the 32-year averages at 67 and 44.

On the warm side, in 2000 the high was 81 with a low of 63. In 1981 the high was 78 with a low of 59. A year earlier, in 1980, the high was 86 with a low of 49, a 37 degree spread. A couple of years later, in 1982, the high was 83 with a low of 51, a 32 degree spread. In 1999 the high was 81 with a low of 53. Another warm high was 79 last year (in 2010). The record high of 92 was set in 1952 and the record warmest low of 66 occurred three years later in 1955. 21 of the last 32 highs (66%) were in the: 50s (8) and 60s (13). On the warmer side, ten highs (31%) were in the: 70s (6) and 80s (4). One high was in the cold 40s. Highs the past two years were in the 70s. Before this, from 2001-2008, seven of these eight years had highs in the 60s. Highs were 81 in both 1999 and 2000.

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: in 1978 the high was a cool 51 degrees. In 1976 the high was 68 with a low of 36, a 32 degree spread. In 1969 the high was a warm 83 with a low of 52, a 31 degree spread and warm day. In 1967 the high was a cold 43 with a low of 33, a cold day. In 1966 the high was 62 with a low of 32, a 30 degree spread. In 1964 the high was 82 with a low of 60, a warm day. In 1962 the high was 83 with a low of 55, a warm day. In 1960 the high was a warm 80 with a low of 54, another warm day. In 1959 the high was 90 with a low of 64, a hot day.

More recently, we had large spreads of 35 degrees in 2002 (69/34) and 30 degrees in 1994 (66/36).

On the cool side, in 1992 the high was 54 with a low of 37. Two years earlier, in 1990, the high was 49 with a low of 43, a six degree spread. Another cool high was 54 in 1996. The cold lows were 33 in 2005 and 34 in 2002. The record low of 32 was set in 1954. The record coldest high of 41 occurred way back in 1907. 25 of the last 32 lows (78%) were in the: 30s (11) and 40s (14). Seven lows (22%) were in the warmer: 50s (6) and 60s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 5:14 and sunrise is at 5:45. Sunset is at 19:56 and twilight ends at 20:27. There's a total of 14 hours, 11 minutes of daylight today and 15 hours, 13 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:13 and sunrise is at 5:44. The moon is waxing crescent, having passed new yesterday at 1:51. Illumination was 1% at midnight, will be 2% at noon and 4% at midnight tonight. Moonrise is at 6:17 this morning. Moonset is at 21:42 tonight. Moonrise is at 7:02 tomorrow morning. Moonlight time is 15 hours, 25 minutes which is 22 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. Mother's Day is in four days. -Bernie-