Last year, I was training for the USAT Duathlon National Championships in Tucson, AZ in late October. I knew the temps would be warmer than in the SF Bay area where I live. So, in the beginning of September, I began putting a thick fleece vest under my cycling jerseys and running tops. Yes, it was uncomfortable for awhile but, as the days went by, my body began to accept the simulated desert heat and to make the necessary adaptations. The science states that cardiovascular adaptation takes place after one week, and sweat response after 2 weeks.
So, you can follow my lead and wear extra clothing; or you can plan some of your workouts to be done in the hottest part of the day; or you can avoid air conditioning whenever possible. Make sure you adjust your hydration needs accordingly and pay extra attention to your recovery from these "hot" workouts.
This is truly a "pay me now, or pay me later" scenario - and I rather arrive at the race start line with one less thing to be concerned about!
400 yds. every 4th lap your choice but 2 of the 4 must be head up swim
6 x 50yds. pull - start the first 50 with a total of 8 breaths and add decrease by 1 for every subsequent 50
12 x 25yds. backstroke golf - count your strokes and add it to the time for the 25 - that is your par - try to beat par for each subsequent 25
6 x 200yds. free or IM - negative split each 200 and progress #1-6
16 x 25yds. odd numbers = fly good effort and even numbers = free recovery + start with 3 dolphin kicks off the wall for the first 25 fly and add 1 kick to each subsequent 25 fly