[theBCnut]

Even if you get freezes, you still need to give heartworm prevention again one month after the last possible exposure. If you don’t get freezes, you are supposed to be able to watch the temp and stop giving when the temp is consistantly lower than whatever temp the larva need to develop. I can never remember what that temp is supposed to be, because whatever it is, we don’t stay cold enough long enough here. But the info is here on another heartworm med thread, if you want to search for it.