In the summer in can be quite hard to keep the gothic look due to the heat.
Summer is not the best time to be wearing heavy wool extensions, so I would recommend using your crimpers and hair pins to go back to your roots. Backcombing your hair is light and looks good. just remember to use hair spray that has good UV filters to protect your hair from fading hair dye.
You might want to swap your usual peroxide based dye for a gentler vegetable based colour, as the sun does not fade these as fast.
Your usual foundation may also react badly to the heat, so a sunblock with titanium dioxide is recommended. This natural mineral is the same white pigment that is found in most powders and foundations. Another tip is to layer some translucent powder over the top.
Waterproof eyeliner is also a good idea to stop panda eyes, and swap your creme eyeshadow for a powder based one to keep everything from sliding off.
Black clothes are still fashionable in the summer months, but stick to fabrics such as cotton, lace, and viscose which are lightweight. A good accessory would be a lace fan to keep your cool.