This is actually a legitimate legal question that has been litigated seriously in federal courts, so it deserves a real answer beyond the obvious jokes about the founding fathers and central air.
The Eighth Amendment prohibits cruel and unusual punishment, and courts have held that prison conditions can rise to that level when they pose a substantial risk of serious harm. Heat is not automatically unconstitutional, but extreme heat has been found to meet that standard in specific circumstances, particularly when combined with factors like high humidity, inadequate ventilation, lack of access to water, and the presence of inmates with medical conditions that make them especially vulnerable to heat-related illness.
The Fifth Circuit, which covers Texas, has issued rulings that extreme heat in certain facilities does constitute a constitutional violation, and litigation over prison temperatures is active and ongoing in several southern states. Florida has faced similar legal challenges. The argument becomes stronger when the extreme heat is documented to cause measurable harm, when vulnerable populations such as elderly inmates or those on medications that affect heat regulation are involved, and when the facility has done nothing to mitigate conditions.
For pretrial detainees specifically, the legal standard is actually higher than for convicted inmates. Pretrial detainees are protected under the Fourteenth Amendment's due process clause rather than the Eighth Amendment, and that standard prohibits punishment of any kind for people who have not been convicted. Courts have applied that protection to conditions of confinement including extreme heat.
One night is anecdotal. Documented patterns of heat-related illness and deaths across Florida facilities are what have driven the litigation. The constitutional question is real, the courts are actively engaging with it, and the answer is not as simple as man up.