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How Sun Season judges the weather

the same rules run on the map, on every destination page and in the where-to-go lists

temperature in · rain in · distances in . Tap a unit to switch.

Sun Season answers one question for any place and month: does the climate fit the holiday you want? It takes 30-year monthly averages of rainfall and of the daily high temperature (WorldClim 2.1, 1970–2000), sorts each month into a rain class and a temperature band, and compares both with a preset such as Beach or Snow. The result is a verdict for every 0.25° cell of land on Earth, for each of the twelve months: good, too cold, too hot, too dry, too rainy or monsoon.

Rain classes

Raw millimetres can mislead: 200 mm in a month is normal in Singapore but a monsoon in Goa. So each month is classed against that place's own year, where P_max and P_min are its wettest and driest months:

Class	Rule
monsoon	≥ 180 mm7.1 in (or ≥ 120 mm4.7 in when that is ≥ 80 % of P_max), and the climate is seasonal: P_max ≥ 3 × P_min
rainy	≥ 100 mm3.9 in and ≥ 35 % of P_max
showers	≥ 60 mm2.4 in
dry	everything else

So a place that is wet all year (Singapore, the west coast of New Zealand) counts as rainy, not monsoon. Monsoon is kept for heavy rain that comes as a season.

Temperature bands

The month's average daily high, in five steps: freeze below 3 °C37 °F · cool 3–19 °C37–66 °F · warm 19–28 °C66–82 °F · hot 28–38 °C82–100 °F · burn above 38 °C100 °F. These are afternoon highs; nights are cooler, and the pages show the low as the other end of a range.

Presets

Preset	Rule
Warm	highs 19–28 °C66–82 °F, dry or showers
Tropical	highs 28–38 °C82–100 °F, any rain except monsoon
Beach	highs 28–38 °C82–100 °F, dry or showers
Cool	highs 3–19 °C37–66 °F, any rain except monsoon
Snow	highs below 3 °C37 °F, any rain

A month fits when its temperature band is inside the preset's range and its rain class is not above the preset's limit. The verdict names the first reason that fails: temperature first (too cold, too hot), then rain (too dry, too rainy, monsoon). Destination pages use the Tropical preset between the tropic lines and the Warm preset elsewhere; on the map you can pick any range.

Data

Rainfall and temperature are WorldClim 2.1 monthly normals for 1970–2000 at 2.5 arc-minutes, aggregated to a 0.25° grid (about 28 km17 mi at the equator). Place names and coordinates come from GeoNames. Everything is served as static files; see the data page.

What this cannot tell you

It is a climate, not a forecast. A 30-year average says what a month is usually like, not what next week will be.
Cells are 0.25° wide. Mountains, coasts and islands smaller than that take the values of their surroundings; a page says "nearest land cell" when the exact point is at sea.
1970–2000 is the baseline. Recent decades are warmer, so real temperatures may be a little higher than the bands suggest.
Averages hide extremes. A dry month can still have a storm; a rainy month can still have sunny mornings.

Who made this

Sun Season is built and maintained by Lauren ten Hoor, a software engineer in the Netherlands, as an independent side project. It began as "Monsoon?", a map that answers one question: is this place in its rainy season right now? That map still runs at monsoon.s3p.dev.