Figure 3 shows the seasonal rainfall for the
different regions of Thailand. Climatologically,
Thailand has a dry season (December to April)
and a rain season (May to September). The south
and east show the highest rainfall. Rain in the
south show a minimum in February and a
maximum in November. There are two rainfall
peaks during the rain season. For the onset, there
seem to show a northwest progression -the early
rainfall peaks first in the east, northeast, central,
and then north regions. The end of the rain
season occurs from north to south, with the
secondary peak occurring in August in north and
northeast regions and in September in central and
east regions, consistent with the movement of the
Intertropical Convergence Zone (ITCZ) rain bands.