[header] How to camp in the rain [title] Bring a waterproofed tent when you know it'll rain. [step] Have a tent with a rain fly that overhangs it so that rainwater drips off the sides. The tent's entrance should form a lip, like a bathtub, so the floor isn't entirely flat. 
Good rain tents are also treated with waterproofing polyurethane or another product. [substeps] Getting a tent with a vestibule is also helpful.