Calculate the NWS heat index (Rothfusz), the Canadian humidex and check whether a heatwave is happening in your city. Map of Spain with today's forecast highs.
| Day | T max | Feels-like max | Over threshold |
|---|---|---|---|
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Open-Meteo data. Colour scale: blue (<25 C), green (25-30), yellow (30-35), orange (35-40), red (40-45), purple (>45).
| Level | Feels-like | Recommendations |
|---|---|---|
| Comfort | <27 C | No special precautions. |
| Caution | 27-32 C | Drink water, avoid intense exercise in the sun. Hat and light clothing. |
| Extreme | 32-41 C | Avoid sun exposure 12-18h. Continuous hydration. Special care for children, elderly, pregnant, chronically ill. |
| Danger | 41-54 C | Heat stroke likely with sustained exertion. Stay in air conditioning. Use municipal cooling centres. |
| Critical | >54 C | Imminent heat stroke risk. Call 112 if confusion, dry hot skin or dizziness. |
According to AEMET (the Spanish Met Office), a heatwave is a period of at least three consecutive days when at least 10% of stations record highs above the 95th percentile of July-August maximums for the 1971-2000 reference period. This is the official definition used to issue operational warnings (yellow, orange or red).
WhatAWeather applies a simplified version of the AEMET rule for a single location: we flag a heatwave when there are 5 consecutive days with feels-like temperature above the 95th percentile of the local climatology. Five days is more conservative and aligns with the WMO definition. The 95th percentile threshold comes from Open-Meteo ERA5 1991-2020 daily history.
The 2022 summer in Spain saw 11,324 excess deaths associated with heat according to the MoMo system (Carlos III Health Institute). The 2003 summer, considered the most deadly recent one, exceeded 6,500 extra deaths. Most are people over 75 with chronic cardiac or respiratory conditions. Heat stroke (core temperature above 40 C, neurological alteration, absent sweating) is the most severe form and requires immediate hospital care.
The IPCC concludes that heatwaves are now more frequent, more intense and longer in Southern Europe. In Spain, AEMET reports that the number of heatwave days has tripled between 1980 and 2020. Projections for 2050 indicate summers 1-2 C warmer on average, with extreme highs 4-6 C above current values in the inland Iberian peninsula.
The NWS Heat Index (Rothfusz, 1990) combines temperature and humidity to estimate the body-perceived temperature in shade. The Canadian humidex (Masterton & Richardson, 1979) follows a similar approach but uses vapour pressure instead of relative humidity, so values tend to be slightly higher in humid conditions.