Generating weather scenarios following Poisson distribution

I would like to generate random values of summer rainfall in Python, for a model of grass growth. I would like to extrapolate a weather series of 42 years that seems to follow a Poisson distribution 1. I tested it in R and it seems to have a Lambda of 4. I didn't find how to generate randomly continuous values (floats) based on my mean precipitation value and assumed lambda. Someone knows how to do that ? Best