@killyourfm how much water are you giving it? especially in extreme heat where the soil drys fast melons need a TON of water, like...absolutely soak the soil (better to water a lot a few times than a little constantly). If it's really hot the soil could be drying too fast before it can really soak it up, or the water might not be penetrating deep enough onto it's roots.
they also do grow VERY slowly, but you should be seeing "something" each week.