Hoi An has two seasons. Dry season runs approximately March until September; rainy season falls from around October until February. In terms of temperature and humidity, February to April is usually the most pleasant. Temperatures soar between May and August, and you’ll learn the reason why the locals do work in the early morning and siesta in the midday.
The high tourist season coincides with Central Vietnam’s wet season, when the seas are rough and at times the rain can feel never-ending. There is a risk of typhoon, and from late October to mid-December Hoi An’s old town is prone to flooding -- the town sits on low ground surrounded by waterways and mountain ranges, and then there’s a tidal influence as the main river meets the sea.
While flooding isn't guaranteed (there were none in 2015), if you are travelling Vietnam during this time and Hoi An is coming up on the itinerary, it’s best to check the latest situation and forecast. Some years it's only knee-high waters on a handful of days; in bad years, the waters have risen up to two metres high and with mudslides in the nearby mountains, it’s been severe enough for the whole region to be classified as a disaster area. If there’s a real risk, then check into a hotel that occupies high ground -- that means most of the guesthouses north of Ly Thuong Kiet Street. Most An Bang and Cua Dai Beach accommodation are safe bets but the popular backpacker accommodation street Ba Trieu is considered in the flood zone.
If for some reason you decide to stay in the flood zone, be sure to request a room above the ground floor. Travel in and out of Hoi An is generally not affected unless there's a typhoon, though many businesses shut their doors during floods, so think twice before prepaying for anything such as cooking classes and tailoring. Before you panic, bear in mind that the typical floods are nothing to be too frightened about -- the waters usually recede almost as quickly as they arrive, and no matter where you are, high ground is never more than a few hundred metres away.
The coldest months are November to January, and combined with the wet coastal weather, it can be downright chilly. It’s not all bad during rainy season though. There are occasional dry spells and warm, sunny days to be pounced on and a day at the beach is not out of the question.
