Weather is probably a major factor when you plan your trip to Greytown, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and May with an average temp of 80°F, while the coldest months are January and February with an average of 77°F. The rainiest months in Greytown are July, November, June, and August, with each month seeing an average of 23 inches of rainfall.