Debra Potvin from Gardnerville wrote in asking why don't they seed the clouds to make rain over Yosemite and other areas where fires are burning ?
Debra I checked with Justin Broglio up at the Desert Research Institute.
We have done a number of stories in the past about cloud seeding operations and how D-R-I uses the technology to beef up snowfall during winter storms.
Unfortunately, that technology doesn't work during fire season. Broglio says one reason is temperature. The silver iodide crystals that they shoot in to the clouds to make snow flakes only work in freezing conditions.
Another factor is moisture. Silver iodide works by joining with existing cloud vapors. But when it comes to smoke clouds the relative humidity is very low in those clouds which prevents the kind of chemical reaction needed for cloud seeding.
So cloud seeding is effective at certain times of the year and it can be used to add to our winter snowpack. But not when it comes to fighting fires.