If something is steamier, it has more steam or feels hotter and wetter.
Steamier can make people think of hot showers, jungles, or cooking food.
Examples:
The bathroom is steamier than the kitchen.
The jungle is steamier than the desert.
The air gets steamier when you take a hot shower.
The soup is getting steamier and steamier!
In the rainforest, it's even steamier than in the bathroom.
The room gets steamier and steamier as the water boils.