GenCast is a new high-resolution (0.25°) AI ensemble model developed by Google DeepMind that is more accurate than the European Centre for Medium-Range Weather Forecasts (ECMWF) ENS system in predicting daily weather and extreme weather events, providing faster and more accurate forecasts up to 15 days in advance. This model is based on diffusion models and represents a type of generative AI model that has recently made rapid progress in image, video, and music generation. GenCast learns global weather patterns by analyzing historical weather data and can precisely generate complex probability distributions for future weather scenarios. The model's code, weights, and prediction results will be publicly released to support a wider weather forecasting community.