Answer:

The weather phenomenon described as "Pitter Patter raindrops" in the poem is light rain.

Explanation:
In the poem, the phrase "Pitter Patter raindrops" is used to describe the sound made by raindrops as they fall. This phrase is often associated with the gentle sound of rain falling lightly on a surface, such as the roof or the ground.

Light rain refers to a type of precipitation that occurs when small water droplets fall from the clouds to the ground. It is characterized by a gentle and steady rain that does not have a significant impact on the environment. Light rain is often accompanied by a soft sound, similar to the "Pitter Patter" mentioned in the poem.

In contrast, a hailstorm refers to a weather phenomenon where frozen raindrops, called hailstones, fall from the sky. Hailstorms are typically associated with thunderstorms and can be accompanied by strong winds and heavy precipitation. The sound produced by hailstones hitting the ground or other surfaces is much louder and more forceful than the gentle "Pitter Patter" sound of light rain.

Similarly, a blizzard refers to a severe snowstorm characterized by strong winds, low visibility, and heavy snowfall. The sound of a blizzard is distinct from the sound of rain, as it involves the howling of winds and the crackling of snowflakes.

Lastly, a thunderstorm is a weather phenomenon that involves the combination of rain, thunder, and lightning. Thunderstorms can bring heavy rain, gusty winds, and lightning strikes. The sound associated with a thunderstorm is primarily the booming sound of thunder, rather than the gentle "Pitter Patter" sound of light rain.

Therefore, based on the description in the poem, the weather phenomenon being described is light rain.