FVFD responded to a mutual aid call in Loleta for a trailer load of hay that caught fire. The trailer suffered a flat tire near Fernbridge, and what the owners didn’t realize was that the flat tire got hot enough, or caused something else to get hot enough that the hay ignited. They didn’t realize it until they got halfway to Loleta. Fortunately they got the truck unhitched from the trailer, but the hay was a total loss. It created a huge amount of smoke and since my approach was downwind I couldn’t even tell what they were trying to put out until later.