MEMPHIS, TN (WMC) - You may think that all rain will wash away pollen, but that is not always the case. Sometimes, certain types of rain can make pollen levels increase.
The rise or fall of pollen levels will depend on how rain develops. Typically, the pollen count may go up right before a storm and it may go down as a gentle constant rain is falling and it may increase again later on.
Rain mostly will bring down high pollen levels, but when it comes to thunderstorms this isn’t always the case. Winds associated with a thunderstorm tends to increase pollen counts as pollen is blown off the grasses and trees. Strong thunderstorm winds and thunderstorms themselves can break up pollen grains into smaller grains that may increase the pollen count. Rain drops can attract pollen grains and take away from the air, but it is based on the size and type of drop some rain drop sizes remove pollen from the air better.
Rain from thunderstorms are not reliable in reducing pollen level and may even raise them. If there is a rain that last a day or two that’s not associated with thunderstorms this may help wash the air clean and reduce pollen counts way more. Typically any storm with wind will tend to increase pollen counts as pollen grains are scattered and broken up into small but still irritating particles. While rain can wash out pollen more or less effectively, it really depends on the rain droplet size. Normally pollen counts will increase after the rain stops.
The rain that comes with thunderstorms can be heavy with large drops. The large drops are not as good at absorbing pollen particles and leave more pollen in the air than a gentle rain does. Violent winds and large rain drops tend to break up pollen into smaller particles, resulting in an increased particle count. These different mechanisms can produce a high level of atmospheric pollen after rain.
Many rain showers that do not come with strong wind or big changes in temperatures. Smaller drops of rain fall gently to the ground and will take a lot of the pollen particles in the air with them. The smaller drops of rain are better at cleaning the air than the larger rain drops in storms. This is due to pollen particles that are absorbed by rain drops through a process known as coagulation.
When these small drops fall, they develop a small electric charge that attracts particles in the air. Small drops also have more surface area per volume than that of large drops. The combination of the electric charge and the larger surface area makes smaller drops effective for cleaning the air.