By Paul Bean

It might sound like a ridiculous question – Do wildfires actually cause more rain?  

Believe it or not: yes, they do – but not in the way you might think. 

The question arose among members of the VDC staff following all this rain and smoke we have been experiencing here in the Green Mountain State over the past few summers. 

Did Canadian wildfires contribute to the heavy July rains that devastated Vermont in 2023 and 2024?

The smoke from wildfires can potentially cause more rain in other areas under specific atmospheric conditions, though the effect is complex and not guaranteed. Wildfire smoke contains tiny particles, such as aerosols and ultrafine particles, which can act as cloud condensation nuclei. 

These particles can enhance cloud formation and influence precipitation patterns when transported to different regions by wind currents. For instance, a 2024 study published on Earth.com highlighted that ultrafine particles from Amazon rainforest wildfires can intensify storm clouds, leading to increased occurrences of heavy rainfall in downwind areas due to their impact on cloud microphysics.

The National Science Foundation reported in a 2022 study that wildfire smoke particles can increase the number of smaller cloud droplets, which, under certain conditions, may lead to enhanced rainfall if these droplets coalesce and grow sufficiently as they are carried to other regions. 

However, this effect depends on factors like the smoke’s chemical composition, humidity levels, and atmospheric dynamics. For example, if smoke is transported eastward from a western U.S. wildfire to the Midwest or East Coast, where conditions might include sufficient moisture, there could be a localized increase in rainfall. 

Historical data from the 2020 western U.S. wildfire season showed smoke plumes reaching the East Coast, with some studies suggesting a slight uptick in precipitation in affected areas, though the impact was modest.

If the smoke-laden air remains too dry or the droplets remain too small to fall as rain, it can suppress precipitation, as noted in the same National Science Foundation study, where smoky clouds produced droplets half the size of pristine ones, potentially reducing rain in some cases. 

As of June 11, with ongoing wildfire activity reported in the western U.S., meteorologists are monitoring smoke trajectories to assess potential rainfall effects on eastern states. Overall, while possible, the likelihood and extent of increased rainfall in other areas depend heavily on local weather patterns and the smoke’s interaction with the atmosphere.

So, to put it in very simple terms: yes, with the right conditions, wildfires can increase rain amounts — but will do the exact opposite if the conditions are the opposite.