I remember summers & milking 100 Holsteins x2 daily, and growing everything it took to feed them year round. Milking was hot but not nearly as hot as the 6000 bale hay loft....in the afternoon....in July. It's big enough that we still have 2 basketball goals installed & many, many games played in it after hay fed out. I learned early to ALWAYS volunteer to learn any/everything that involved driving a tractor. Worked earlier & later many days but anything beat stacking hay in that loft under the tin roof. Still no ac in the farmhouse and not sure how my brothers & I survived Summer's together in the "boy's room." Box fans helped a little, I guess.
And yeah, heat must not have been quite as hot "back then."