First and foremost, it is travelers to Africa, south of the Sahara, who need malaria medicine. One should not travel here without malaria medicine.
In South Africa, it is only in the north-eastern part (especially the Kruger Park) that malaria medicine is needed from October to May.
Outside of Africa, there are very few places where it is unsafe to travel without malaria medication, and it will usually be sufficient to protect yourself from mosquito bites (with mosquito spray, covering clothing and permethin-impregnated mosquito nets), and to seek medical attention as soon as possible if you experience symptoms such as can indicate malaria such as fever, frostbite, headache, muscle pain and general feeling of illness.