I saw Mr. Wizard do that once. ;-)
Many many years ago, in "Ripley's Believe it or Not" or some equivalent publication, there was a story that claimed that a boxcar full of steel wool was set on fire by snow.
The snow got into the cracks between the car's timbers and started oxidizing the steel wool, causing it to heat, igniting the whole batch.
But I haven't been able to verify or refute this - I read about it about a half-century ago.
Cheers! Rich