Final answer:
The weather in May is most similar to the weather in October. Both months typically have mild temperatures and moderate precipitation, and are in the shoulder seasons.
Step-by-step explanation:
The weather in May is most closely related to September. During these months, Earth leans "sideways"—neither into the Sun nor away from it. This position means the two hemispheres are equally favored with sunshine, and consequently, the weather is similar. Unlike February, October, or January, which are more characteristic of the colder seasonal weather in the Northern Hemisphere, and unlike July, which is typically hotter, September offers a moderate climate that often resembles that of May.