What is the maximum difference in oxygen content in the air between a rainy day and a sunny day?

The water vapor content in the air is high on rainy days, but the content of dust, harmful gases and other pollutants in the air will be much reduced after being "washed" by the rain.

On a sunny day, sunlight can disinfect and sterilize the air, so there are fewer viruses and bacteria in the air; photosynthesis is strong, and plants release more oxygen.

So sunny days after rain are the best.