El Nino Watch

Heat stress (days with feels-like above 35 °C)

How many days a year the feels-like maximum exceeds 35 °C (ERA5, 1991-2020 average). Humid tropical places score high even when the air temperature looks moderate.

Hazards

Counted from ERA5 daily feels-like (apparent) maximum temperature, averaged over 1991-2020. Feels-like uses temperature, humidity and wind, so humid heat counts more than dry heat.

Why it matters for Koh Samui

Heat stress affects sleep, health (especially for older people and children), work and electricity bills for air conditioning. El Nino years add heat in Southeast Asia.

Thresholds

Heat days per yearExposure
< 50 very low
5-301 low
30-902 moderate
90-1803 high
>= 1804 very high

Exposure scale: 0 very low, 1 low, 2 moderate, 3 high, 4 very high. Higher = more exposed. The colour of the matrix cell follows the same scale.

Sources

Related

ENSO status now

ONI (NOAA CPC)
+1.80 °C, JJA 2026 (previous +1.39 °C)
RONI (NOAA CPC)
+1.36 °C, JJA 2026
Nino 3.4 weekly (NOAA CPC / OISST)
+3.0 °C anomaly, week of 16 Sep 2026 (SST 29.6 °C)