Planning for the weather is a good way to make your trip to Greytown relaxing and enjoyable, especially when you're splurging. The hottest months are usually September and May, with an average temperature of 27°C, while the coldest months are January and February, with an average of 25°C. The rainiest months in Greytown are July, November, June and August, with each month seeing an average of 582 mm of rainfall.