El Nino Watch
NASA's daily satellite-and-model weather for the Samui grid cell, with 2001-2020 normals.
Data and trust
NASA Langley's POWER service combines the MERRA-2 / GEOS-IT weather reanalysis with CERES satellite sunshine data. The app asks it twice a day for the last 60 days of temperature, rain, humidity, wind and sunshine at 9.512 N 100.013 E, and for the 2001-2020 monthly normals of the same place.
Limits. One grid cell is about 50 km across and mixes sea and land, so it smooths out the island's own showers and hottest afternoons. Use trends, not single days.
Values are daily, in local solar time: degC, mm of rain, % humidity, m/s wind, and kWh per m2 per day of sunshine. Temperature and rain arrive about 2-3 days late, sunshine about 5-7 days late. Missing days are simply absent (NASA marks them -999 and the app never stores those).
It is an independent second source next to Open-Meteo/ERA5: if both say the last weeks were drier and hotter than normal, the signal is solid. In El Nino years Samui often gets a weaker, later rainy season (normally October-December).