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And then the rains started. May marks the onset of Thailand's primary monsoon season, and by the end of April you'll be counting the hours till May 1. Pretty much the entire country sees a significant rise in rainfall — some areas more than others — and you can expect most every province to have at least some rain every other day. This isn't good news if you've just arrived, but it makes for a very welcome relief for anyone who was in Thailand in April!
May is a wildcard. In some years it feels like an extension of hot season while in others it truly marks the beginning of rainy season. The haze lifts over Northern destinations like Chiang Mai and Lampang, where a few good storms render the mountains a lush shade of green. It’s a great time to watch rice farmers sewing their fields in Northeastern points like Ubon Ratchathani and Nakhon Phanom. This is also when Yasothon holds its wild Bang Fai (Rocket) Festival. Fruit season is in full swing in eastern Gulf provinces like Rayong and Chanthaburi, which holds a durian-eating contest as part of its annual fruit festival.
The lower Gulf islands of Ko Samui, Ko Pha Ngan and Ko Tao see significantly less rain than other parts of the country in May. The Andaman Sea islands and eastern Gulf islands shift into low season, with some resorts on smaller islands like Ko Bulon Lae and Ko Wai closing up completely. In these regions, the seas begin to get rough and many public ferries cease operating until November.
May sees the first of a series of falls in temperature from the April peak. It will still be very warm across the country, and, when combined with the rain, the humidity can be excruciating, but the rains do provide relief all too frequently. Expect to see some flooding in urban centres like Bangkok in the first weeks of the rainy season as drains, all clogged up with dry season debris will block.
Ko Chang in May is wet. Not as wet as it will get in the coming months, but certainly wetter than just about any other island in Thailand — if you really want some island time but don't want to head south, Ko Samet is a better bet. Back on Ko Chang, expect at least some drizzle most days. On the upside the crowds from April will start to drop off.
The rains start midway through May in Chiang Mai and it quickly ramps up to rain every other day. As elsewhere this provides welcome respite from the heat of April, but an added bonus is that it starts to clear the air, taking at least some of the smoke back to earth. The regions many waterfalls start to get going again and trekking starts to get a little bit more, well, slippery.
May sees a slight dip in temperatures and a pretty much doubling of rainfall from the preceding month in Thailand's northeast. That said, given how hot it was in April, May remains a very warm month. Expect rain every other day.
Unlike the rest of the country, in May there is a small hike in temperatures, but as with near everywhere else there is a substantial increase in the rainfall. The northern section of the Gulf Coast sees less rain than Ko Samui and surrounds, so if you're after some beach time and are not fussed about heading out to an island, sticking to an area like Hua Hin should see you get slightly better weather — but you won't be bone dry.
Only Ko Chang gets more rain than Phuket, Krabi and surrounds in May. Temperatures are only slightly off from the highs of April, so you'll still be hot — just wet as well. It's not all day torrential affairs, but expect a heavy downpour for an hour or two most days. In between the rains, if you're in luck, you'll score some brilliant sunshine. May sees the commencement of very good deals for hotels on this coast, so if you're willing to gamble on getting wet, you can get some fabulous hotel deals on Phuket and Ko Phi Phi.
Follow the links below for a Thailand weather summary for each month of the year.