How mushrooms make it rain . . .

A single mushroom can “catapult” up to 30,000 spores per second at speeds of up to 4mph. There are around a billion mushroom spores above every square metre of Earth’s surface. These spores provide a scaffold for water to condense and seed rain droplets. 

When it comes to rainmaking power, fungi spores are number one.
Other types of particles such as pollen, bacteria, dust and pollution also seed rain, but scientists have seen what makes mushroom and other fungi spores such potent rainmakers.
Under an electron microscope, scientists saw water droplets form on the water-attracting spores in humid air. Over time, those droplets evolved into large water drops that may produce rainclouds.
The effect of spore rainmakers is efficient production of rain over forests, even during warmer months. Plus, the process does not seed rain using pollutants, which is beneficial to ecosystems.
See this video for more info or check the research article on this link.

Article Source: Cosmos Magazine​
Video source: Minute earth