The state song proclaims that the "sun shines bright on my old Kentucky home," but all bets are off when it comes to nice weather for the Kentucky Derby.
Of the 137 Derbys run so far, nearly half — 63 — experienced rain at some point during the day, according to the National Weather Service office in Louisville.
Nevertheless, the generally good weather experienced in early May is a primary reason the Derby is run on the first Saturday of the month. The average temperature for Louisville in early May is 74 or 75 degrees.
The Kentucky Derby has never been canceled because of weather, although it was postponed to June 9 in 1945 because of a wartime ban on racing.
In its first decade, the Derby was run in the latter half of the month, with dates ranging from May 15 in 1876 to May 23 in 1883.
But when Matt Winn and several other men purchased the financially troubled Churchill Downs in 1902 for $40,000, he wanted to turn the Derby into a tradition, and he wanted a good day for it.
Winn studied the weather conditions of Louisville as far back as he could and determined that the first Saturday in May was the prettiest day of spring.
Sure enough, the skies were clear and the track was deemed fast for the Derby on May 2, 1903. The track turned a profit for the first time in its history that year, and Winn became general manager in 1904.
But thunderstorms threatened the 1905, 1906 and 1908 Derbys, according to National Weather Service records.
Today, some might question Winn's decision about the first Saturday in May. The longest stretch of consecutively dry Derby Days happened in the race's very beginning, from the first in 1875 to the 12th in 1886. Only a trace of precipitation was recorded on the 13th Derby in 1887.
The wettest Derby was in 1918, when 2.31 inches of rain fell — an inch of which fell from 1 to 7 p.m. It was the first Derby in 22 years in which the track was deemed "muddy," but that didn't prevent Exterminator from winning by a length.
A sloppy track means bettors must evaluate the race in a manner that gives preference to "mudders," those horses that perform better on a wet surface.
Take, for example, the 50-1 shot Mine That Bird in 2009. The gelding, ridden by Calvin Borel, shocked everyone by skimming through the slop close to the rail and winning the Derby by 6¾ lengths. It was the largest margin of victory since Assault won by 8 lengths in 1946.
Compare that to General Quarters, who came in 10th in 2009's field of 19 horses.
"He came back to the barn choking in mud," trainer Tom McCarthy said after the race. "One eye was completely shut with mud. He coughed twice, and it popped out."
In many cases, Derby horses don't have experience with mud, and it's impossible to tell how the 3-year-olds will react when the gate opens.
"It hits their belly and face," trainer Bob Baffert told The Associated Press in 2010. "They throw their head up, they lose interest and they get scared."
The longest stretch of consecutively wet Derby Days was from 1989 to 1994.
Of the most miserable Derby Days, 1989 was among the worst. It rained lightly and then sleeted for about four minutes just after 1 p.m. It was 43 degrees at race time.
A mint julep vendor who had been handling trays of the ice-filled drinks all day told the Herald-Leader: "My fingers are so frozen, I can barely count my money. I'm afraid someone's going to grab my money and I won't even feel it."
Arrests in the infield were well below normal that year as the cold put the kibosh on disorderly conduct, but sales of official Derby sweatshirts were up.
Attendance for the 1989 Derby was 122,653, or about 15,000 less than the year before, when the high was in the low 80s.
The coldest temperature recorded on Derby Day was 36 degrees in 1940 and 1957 (the Weather Service notes that the lows weren't necessarily at race time). The 1957 Derby was accompanied by 20 to 25 mph winds.
At the opposite extreme, the warmest temperature recorded on Derby Day was 94 degrees in 1959. British Ambassador Sir Harold Caccia, in attendance that day, was quoted in the Lexington Herald as saying the warm, sunny weather was welcome compared to what was typical at the English Derby, or "Darby."
"At the Darby, it's always raining," Caccia said.
The sports page of the Herald showed a from-the-neck-up photo of Bill Shoemaker, the jockey aboard 1959 winner Tomy Lee, enjoying a shower after the hot day.
What this year's Derby will bring is anyone's guess. During the past 10 years, the weather has ranged from thunderstorms in 2010 to mostly sunny in 2002 and 2005.
The only sure thing is this: Whatever the weather for Derby Day, umbrellas are a "banned item" and cannot be taken into Churchill Downs.
Greg Kocher: (859) 231-3305. Twitter: @HLpublicsafety.