LOUISVILLE, Ky. – Before dawn Sunday morning at Churchill, the wearing of a parka wouldn’t have been entirely absurd. Pockets of truly cold air drifted through the darkness. Three days later, the Downs has turned subtropical. The temperature Tuesday night didn’t drop much below 70 degrees, and the mercury was expected to hit 90 late Wednesday afternoon. The heat wave is forecast to continue all the way through Derby Day, though forecast highs for Saturday have come down from 87-89 to the 85-degree range. But the chance still remains for 2012 to be the hottest Derby in recent history. The highest temperature on any Derby Day since 1973, Secretariat’s year, is 86, recorded in 2001 and 1987. Only seven times in the last 39 years has the Derby Day high temperature risen into the 80s. Most of the time, the air has been something like a pleasant 73 degrees when the crowd begins to sing My Old Kentucky Home. Heat affects horses in different ways. During Tuesday’s Derby and Oaks training session, Union Rags had begun sweating significantly soon after making his way onto the racetrack. By contrast, I’ll Have Another and Done Talking barely had broken a sweat, even after galloping more than 1 1/2 miles. John Ward, who trained Monarchos to his 2001 Derby win, said he didn’t remember the extreme heat compromising either his horse or anyone else’s before the race. “We had just come out of Florida, so we were used to it,” Ward said. “Monarchos didn’t get hot, and in the paddock, I do remember thinking all the horses weren’t really affected by the heat. When you leave the paddock and go out the tunnel and onto the track at Churchill, the air starts to move around again, and whatever sweat they have on them will dry off.” The exception to that, Ward noted, is a horse that’s truly nervous. Then, the sweat keeps coming – and the bettor is well advised to act accordingly. [KENTUCKY DERBY: Get PPs, watch analysis video, read latest updates] [KENTUCKY DERBY FIELD: Watchmaker's odds, video contender profiles] [KENTUCKY DERBY WORKOUTS: Latest updates, Mike Welsch's video reports]