I'm a weather nerd. This is my usual spiel for that period:
In June/July normally all Thailand except the southern Gulf is in monsoon. The southern Gulf (Samui and neighbours plus adjacent mainland coast) usual wet season is Oct into Jan. I have had some great holidays there mid year - lots of sunshine, a few good storms.
June/July is normally not the worst of the wet season most other places - Sept and OCt tend to be wetter. I know one Phuket
expat says the real wet season does not start until sometime in late July or even later. I have had good holidays both midyear and in August in the Andaman. Usually plenty of sunshine, one or more showers/storms per day, quite a few days with no rain or rain only at night, prolonged rainy periods not real common.
My experience of wet season months is that 15-25% of days tend to be blowy which can make west facing beaches and ferry trips unpleasant and longtail snorkelling trips cancel.
However quite a few wet season days have little or no wind and when the sun's out conditions on those beaches can be as good as anywhere.
"Anywhere I should avoid?".
Well the eastern Gulf around Trat/big Ko Chang
is often REAL wet in June - the AVERAGE is over 900mm for the month - I'd hate to be there in a wetter than normal June. For comparison, I think London averages something in the 400s for a YEAR. Nevertheless I've seen plenty of posts from Chang in mid-year talking of good holidays - looks like they still get a fair bit of sunshine, but when it rains it REALLY rains.
I've also seen a number of posts talking of PEOPLE DROWNING in big surf on Chang. All the main beaches face west into the prevailing winds - when these blow hard for a few days you can get big surf with dangerous rip currents, so take care. Maybe you could read my TIPS ON NOT DROWNING PAGE here http://tezzasthaiinfo.blogspot.com/2007/04/some-tips-on-not-drowning.html
area is also extra wet at around 700mm. I think the tourist attractions there,Ko Phayam and little Ko Chang Andaman side largely close down in the wet season.
BTW, the central Gulf, Ko Samet, Pattaya and Bangkok often get less rain than most areas besides the southern Gulf in JuneJuly.
#3 tezza has been a member since 13/4/2006. Posts: 1,339