Beat the heat and use it as a means to dye your fabrics for you, easy peasy!
Lay out your fabric, sprinkle with dye stuffs such as onion skins, finely ground tree barks, walnut shells, etc., wrap tightly, soak with vinegar, wrap tightly in aluminum foil, or plastic wrap, and place in a sunny area that gets really hot, like your garden shed roof, or deck off of your house.
Allow to remain bundled for a couple of days.
After a couple of days open your bundle and allow to air dry.
After it's "cured" open your bundle, remove the vegetation, and rinse your bundle prior to washing.
I wash my fabrics with a gentle detergent.
To learn more check out my eBook Compost Dyeing and Other Fermentation Dyeing Techniques.