The heat is a training variable, not an excuse
From June to September, outdoor work before 8am or after 8pm is the honest window. Everything else moves indoors.
Hydration, specifically
Most people show up already down a litre. Drink 16-20oz in the two hours before a session and add electrolytes if you sweat heavily — plain water alone will leave you flat.
Swap, do not skip
Hill sprints become bike intervals. Long outdoor walks become weighted carries in the garage with a fan on. The stimulus survives; the location changes.
Lower the intensity ceiling
In 105 degree heat, your usual top set is not your usual top set. Cut load by 10-15 percent and keep the reps clean. You lose nothing over a summer by training slightly lighter and finishing every session.