Don't overcrowd your venues. Provide a chill out room. Couches, bean bag chairs and ambient music make a comfortable environment for people to relax and cool down after dancing energetically. Establish proper ventilation and temperature control measures. Air conditioning may not be available, but large fans, open windows and doors can often do the job.
Fans blowing hot air from the inside out through an open window are better than from the outside in.
Also remember that hot air rises. The heat on the dance floor wants to go up. Ceiling vents with exhaust fans provide the best ventilation. Provide safety and harm reduction information to your patrons. Have your security trained in basic first aid, and hire onsite EMTs for events with more than 500 people attending.