Rainwater usage for drinking and cooking purposes is legal in Wyoming, but it is important to consider health concerns before doing so. Rainwater can contain contaminants such as bacteria, viruses, and chemicals that can be harmful to human health. Therefore, it is recommended to properly filter and treat rainwater before consumption. Additionally, some cities may have regulations on rainwater usage, so it is important to check local guidelines. It is important to note that while rainwater can be a viable source of water for off-grid living in Wyoming, it should be properly managed and maintained to ensure safe usage.