April 30: ORD

Today is April 30th. It's the 120th day of the year. 245 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 64 and the normal low is 42. I've calculated the 32-year averages at 62 and 43.

On the warm side, last year (in 2010) the high was 81 with a low of 62. In 2001 the high was 85 with a low of 50, a 35 degree spread. The only other 80s high in O'Hare's history was 84 in 1962. Other warm lows were 57 in 1986 and 54 two years ago (in 2009). The record high of 91 and record warmest low of 68 were set on the same hot day in 1942. 26 of the last 32 highs (81%) were in the: 50s (10) and 60s (16). On the warmer side, four highs were in the: 70s (2) and 80s (2). On the cold side, two highs were in the 40s. Last year was the warmest April 30 of the past 32 years. Here's a rundown: O'Hare: 81/62, Midway: 82/62, McHenry: 79/53, DeKalb: 79/56, Barrington: 78/58 and at the Chicago Botanic Gardens in Glencoe: 84/60.

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 48 with a low of 35, a cold day. In 1977 the high was 71 with a low of 39, a 32 degree spread. In 1970 the high was 71 with a warm low of 66, a five degree spread and warm day. In 1968 the high was 72 with a low of 42, a 30 degree spread. In 1964 the high was a cold 49 with a low of 45, a four degree spread. In 1963 the high was a cold 51 degrees. In 1962 the high was a warm 84 with a low of 49, a 35 degree spread and warm day. In 1961 the high was 67 with a low of 36, a 31 degree spread.

More recently, we had a small spread of seven degrees in 2006 (59/52). The large spreads were 35 degrees in 1985 (75/40), 34 degrees in 2000 (71/37) and 31 degrees in 1988 (69/38).

On the cold side, in 1994 the high was 43 with a low of 34. In 1979 the high was 47 with a low of 35. Other cool highs were 50 in 1995 and 52 a year later in 1996. The record low of 30 was set way back in 1873. Three years ago (in 2008) the low was a near-record 31 degrees. The record coldest high of 39 occurred way back in 1907. 24 of the last 32 lows (75%) were in the: 30s (12) and 40s (12). Eight lows (25%) were in the warmer: 50s (7) and 60s (1). The first 60s low (of the past 32 years) occurred last year (in 2010) at 62 degrees. This was just the second 60s low in O'Hare's history (the other was 66 in 1970).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 5:20 and sunrise is at 5:51. Sunset is at 19:51 and twilight ends at 20:22. There's a total of 14 hours of daylight today and 15 hours, 2 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:19 and sunrise is at 5:49. The moon is waning crescent. Illumination was 8% at midnight, will be 6% at noon and 4% at midnight tonight. Moonrise is at 4:14 this morning. Moonset is at 17:42 this afternoon. Moonrise is at 4:39 tomorrow morning. Moonlight time is 13 hours, 28 minutes which is 37 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. National Teacher Day is in three days. Mother's Day is in eight days. -Bernie-