Monthly rain and heat charts (aligned by water year)
Every event drawn on the same 12-month axis from June of the developing year to May of the next, with the 1991-2020 monthly normal as a band and 2026 as the thick line that stops at the last complete month.
Koh Samui watch
The horizontal axis is the island's water year: June to September (southwest monsoon, the event grows), October to December (northeast monsoon, the refill), January to May (the dry season after the peak). "Y" is the year the event started, "Y+1" the next one.
Rain chart: monthly ERA5 rain in mm for each event; the shaded band is the 1991-2020 normal of the same month (the light band spans 75% to 125% of it). A line under the band in Oct-Dec means a weak refill; under it in Feb-Apr, a hard dry season.
Heat chart: the hottest feels-like day of each month; the dashed line is the 1991-2020 normal of that monthly maximum. The 39 °C reference line is the risk engine's heat "watch" threshold.
Use the legend to hide or show events; hover or tap a month for every event's value. "Show table" gives the same numbers as text.
How to read it
Look for where a line leaves the band and how long it stays out. The 2026 line only covers complete months (a month needs at least 25 valid days), so it ends before the newest partial month.
Why it matters for Koh Samui
The shape of the year matters more than one total: 2015-16 had a normal refill and still a very dry Feb-Apr; 1991-92 and 2009-10 were dry from October on.