How SeasonMap scores climate comfort

1. Eight climate factors

For each destination and month we start from long-run monthly climate normals and score eight factors from 0 to 100: temperature (using the apparent / “feels-like” high where available), humidity, rainfall, sunshine, daylight, wind, snow, and air quality (mean US AQI). Each factor degrades gracefully — if a metric is missing for a place, it contributes a neutral score rather than breaking the result.

2. Travel-style weighting

The factors are blended into a weighted average, and the weights — plus the ideal temperature range — change with your travel style. A beach trip prizes warmth, sunshine and low rain; a city walking trip prefers mild temperatures; hiking rewards clear, dry, temperate conditions; winter / snow inverts the usual cold penalty so reliable snow counts as a plus. You can also tune the weights and ideal range yourself.

3. A feasibility penalty for genuine extremes

A plain weighted average can be fooled — a dry, sunny desert at 42 °C would “average away” its heat. So a feasibility factor multiplies the score down hard when conditions are genuinely unlivable (punishing heat, extreme cold), so a place can't look pleasant on paper when it isn't in practice.

4. Seasonality — this month vs. the other eleven

A month's comfort is also ranked against the destination's own other eleven months, and the final score is a variance-aware blend: places that are pleasant year-round barely use seasonality, while strongly seasonal places lean on it. That's why each destination has a clear best and worst month, not a flat line.

5. Tiers

The final 0–100 score maps to a letter tier for quick scanning — S and A are excellent, B/C are decent-to-mixed, and D/F flag months to avoid.

Where the numbers come from

Every place carries twelve monthly normals built from the last ten years (2016–2025) of daily data — recent enough to reflect the climate as it is now, long enough to average out a freak year. Two kinds of source go into them:

• Weather-model reanalysis for every place and every variable: ERA5 and ERA5-Land from the Copernicus Climate Change Service (ECMWF), read through Open-Meteo with elevation downscaling on the Copernicus DEM. Sea temperature is ERA5's ocean component; air quality is the monthly mean US Air Quality Index from the CAMS global reanalysis.
• Weather stations to correct the model where an instrument actually stands: daily records from NOAA's GHCN-Daily (quality-controlled national and cooperative networks) and Global Summary of the Day (the synoptic stream, for dew point and wind). For roughly three places in four a station within 30 km and a similar height qualifies; its ten-year record is compared with the model at the station's own location, and that difference — the model's bias, not the station's microclimate — is applied to the place. Rain corrections use real gauges only, temperatures are adjusted for height with the standard lapse rate, and every correction is clamped so one odd instrument cannot distort a place.

Why bother? Reanalysis models flatten the day: checked against 1,011 stations, ERA5 ran 1.6 °C too cool on daily highs (2.4 °C on islands) and over-counted wet days by about three a month. After correction the residual is 0.1 °C. Hot places used to look more comfortable than they are; now Yazd's August high reads 39.5 °C, as the Iranian normals say, not 35.9.

Contains modified Copernicus Climate Change Service and Atmosphere Monitoring Service information (2026). Station data courtesy of NOAA National Centers for Environmental Information. Neither endorses this product.

What the weights are anchored to

The travel-style weights and ideal temperatures are not guesses; each style is calibrated to published research on what people actually find comfortable:

• City walking — the Holiday Climate Index for urban tourism (Scott, Rutty, Amelung & Tang, Atmosphere 2016): thermal comfort 40%, rain 30, cloud 20, wind 10, optimum 23–26 °C.
• Beach — HCI:Beach (Rutty et al., Atmosphere 2020): sky conditions outweigh temperature, a warmer optimum, and swimmability from sea-temperature comfort guides (20–26 °C).
• Winter / snow — the Ski Climate Index (Demiroglu et al., Int. J. Biometeorology 2021): snow reliability first, comfortable days −7…2 °C, strong wind ruins a day.
• Running — marathon physiology (Ely et al. 2007; El Helou et al. 2012, 1.8 million finishers): performance peaks around 10–12 °C and falls with heat and humidity.
• Hiking — hiker preference surveys (Martínez-Ibarra & Pardo): 15–19 °C, no rain, low wind, clear views.
• The original Tourism Climate Index (Mieczkowski 1985) corroborates the overall balance of daytime comfort, sun, rain and wind.

Limitations

• These are normals, not a forecast — they describe a typical month, not the weather on your specific dates. Any given year can differ.
• A monthly mean hides the days. A place with a 24 °C average can be 18 °C on Tuesday and 31 °C on Friday; we don't yet score that spread.
• Places without a nearby station — many mountain resorts, trekking hubs and parks — rely on the model alone. Snowfall is the least reliable metric everywhere; treat snow scores as directional.
• Comfort scoring is opinionated by design — which is exactly why the weights are yours to change.