I agree w/ anna 66. I also give my dogs heartworm meds year round just in case the skeeters come out early. Also my dog are on interceptor which also protects against hookworms, roundworms & whipworms which they can get any time of the year. I would rather be safe than sorry. It is worth the life of my pet & not to mention cheaper & easier than treatment which is ussually at least $1000.00.