Thailand experiences a tropical climate dictated by Monsoons which in turn produce 3 distinct seasons each year everywhere in the Kingdom except the most southerly reaches on both sides of the peninsula, where 2 seasons are typical. Generally the weather in Thailand is extremely hot and humid, with temperatures ranging between 30 - 40°C with the exception of a small window of ‘relief’ which comes between December and January where in the North (including Chiang Mai and surrounding areas) temperatures may drop to as low as 10°C in the hills, in addition to Bangkok and the central regions where temperatures may drop several degrees; still a welcome relief after a scorching ‘hot season’! Humidity is high generally hovering between 60 and 80% during the dry and wet seasons.
Between May and November, this period is known as the rainy season in most parts of the Kingdom with the exception of Koh Samui where it is dry and sunny for the majority of this period (Koh Samui Seasons). During this time the rain is sporadic but heavy and flooding is common, however, between rain storms the sun typically comes back out, the flood water disperses, everything dries out and life returns back to normal. With clouds often seen building throughout the late afternoon, the rain frequently falls during the early part of the evening.
Nov – May: Dry
During November and May, Thailand experiences little in the way of rainfall and can be split into two distinct periods; dry & hot and dry & cool.
Nov – Feb: Dry & Cool
During November as the rains begin to subside, the weather becomes noticeably cooler, particularly in the evenings when drops of several degrees occur. However, still proceed with an air of caution as the cool season should be by no means considered ‘cool’, rather ‘cooler’ as evening temperature still range around the 26 – 28° mark (still pretty hot in many peoples view), but after experiencing 35 - 38° during daylight hours and mid 30°’s during the hot season evenings, this difference is quite noticeable and comes as a major relief.
During December and January the drop in temperature and humidity is even greater. It is during this time that al fresco dining, drinking, and open-air shopping come into major effect, particularly in Bangkok where up until this point most people have been hiding in the relative coolness of air-conditioned hotels, restaurants, shopping malls and bars.
Feb – May: Dry and hot
Between February and May, this is when things really hot up! Day time temperatures are several degrees higher than the dry cool season (and every single degree counts when temperatures are in the mid – high 30’s). And, the evenings don’t see much let up as temperature stand their ground remaining in the upper 30°C’s. This can lead to some uncomfortable nights if you plan to spend a lot of time outdoors and don’t dress sensibly. Needless to say, air-conditioning for most is an essential component of day to day life during this period.
During this period, Koh Samui is at its driest and sunniest with minimal rainfall. Temperatures vary, but tropical heat is guaranteed. The hottest months are during March and April.
Jan – Mar & May – Sept: Dry & Sunny
During this period Koh Samui is at its most pleasant experiencing less fierce heat and typically dry conditions, but be prepared to rub shoulders with most of Europe!
Mar – April: Dry & Hot
During this part of the season the weather is at its hottest with temperatures peaking in the high 30°’s.
Oct – Jan: Rainy
WConsidered the rainy season, October to January experiences the highest rain fall but is well equipped to deal with it. A general pattern which includes intermittent doses of heavy rain followed by ample amounts of sun, this certainly doesn’t deter happy holiday makers from venturing to Koh Samui and the surrounding islands during the Christmas and New Year period.
The 2 season cycle is limited to only the most southerly parts of the Kingdom and consists of simply a dry and a wet season, although rain does generally fall intermittently during the year.
Nov – May: Dry
This period is typically when the least rain falls in the region and the seas are at their calmest making it most suitable for watersports including diving and snorkeling and island tours. Featuring the most reliable weather, this is the period known as the ‘high season’ where beach resorts, hotels, restaurants, bars, shops and island infrastructure are operating in full flow everywhere in the region.
May – November: Wet
This period is ‘usually’ when most of the rain tends to fall, although it’s not uncommon in previous years for rainy seasons to be dryer than the actual dry season itself. However, more often than not, the rainy season does deliver the goods. Characteristics include not only rain, but also high winds and choppy (and sometimes dangerous) seas. On islands other than Phuket, (e.g. Koh Lanta, Koh Phi Phi & Koh Yao), operations often slow right down with some shops, bars, restaurants closing during the period. Watersports, including diving are generally not worthwhile as visibility is low and the journey out to the dive site often bumpy. That said, this is the season known as the ‘low season’ in hotelier terms, and is when resorts and hotels are at their most reasonable, price wise. So, if you prefer peace and quiet, kicking back with a good book whilst experiencing the sporadic and unpredictable nature of the elements at this time of year, (including plenty of sunshine!), this is the time to come.
High Season: If you had to pick a best time to visit Thailand, it would probably be between November and March. Bangkok and the North are cooler (particularly in December and January), making all outdoor pursuits day and night much more comfortable and enjoyable and the islands in the south are fully functional with all facilities and tourist attractions operating in full flow.
However, if you wish to include Koh Samui in your trip to Thailand, October to January are actually considered the rainier months of the year. So, in order to combine Bangkok and Koh Samui, the end of January until March is one of the best periods to consider.
Low Season: If you fancy an even better deal than those on offer during the high and peak seasons, why not try the off-season where numerous bargains can be snapped up. During this time, particularly on the lesser developed islands, aside from the attractiveness of the price, one can virtually have a beach to oneself and locals have more time to mingle enabling tourists to really get insight into real island life.