Heat index calculator
Regions and countries use reference points; choose a place for a local result.
The heat index combines air temperature and humidity into how hot it feels in the shade. 33°C (91°F) at 65% humidity feels like about 41°C (106°F) — danger.
Right now in London · Heat index8.8°C · 47.8°F
- Temperature: 9.1°C · 48.4°F
- Relative humidity: 90%
- Heat index applies from about 27°C (80°F)
- Model “feels like”: 6.7°C · 44.1°F
Heat index risk levels (US National Weather Service)
| Heat index | Level |
|---|---|
| < 27 °C (80 °F) | Below caution level |
| 27–32 °C (80–90 °F) | Caution |
| 32–39 °C (90–103 °F) | Extreme caution |
| 39–52 °C (103–125 °F) | Danger |
| ≥ 52 °C (125 °F) | Extreme danger |
Heat index right now by country (capital cities)
| Place | Temperature | Relative humidity | Heat index | Level |
|---|---|---|---|---|
| Bahrain | 28.8°C | 70% | 32.3°C | Extreme caution |
| Papua New Guinea | 28.7°C | 71% | 32.3°C | Extreme caution |
| United Arab Emirates | 27.4°C | 87% | 31.6°C | Caution |
| Trinidad and Tobago | 27.6°C | 81% | 31.3°C | Caution |
| Ghana | 27.1°C | 88% | 31.0°C | Caution |
| Thailand | 26.8°C | 92% | 30.9°C | Caution |
| Maldives | 27.5°C | 79% | 30.8°C | Caution |
| Jamaica | 27.2°C | 85% | 30.7°C | Caution |
| Senegal | 27.1°C | 85% | 30.5°C | Caution |
| Indonesia | 26.8°C | 83% | 29.6°C | Caution |
| Fiji | 27.7°C | 65% | 29.5°C | Caution |
| Philippines | 26.5°C | 87% | 29.1°C | Caution |
| Sudan | 30.1°C | 31% | 28.9°C | Caution |
| Kuwait | 27.0°C | 60% | 28.1°C | Caution |
| Cambodia | 25.9°C | 93% | 26.4°C | Below caution level |
| Singapore | 25.9°C | 93% | 26.4°C | Below caution level |
| Bangladesh | 25.9°C | 84% | 26.3°C | Below caution level |
| Oman | 26.1°C | 65% | 26.3°C | Below caution level |
| Macau | 25.3°C | 87% | 25.7°C | Below caution level |
| Hong Kong | 25.3°C | 85% | 25.7°C | Below caution level |
| Mexico | 26.0°C | 24% | 25.6°C | Below caution level |
| Brunei | 25.1°C | 95% | 25.6°C | Below caution level |
| Angola | 25.2°C | 86% | 25.6°C | Below caution level |
| Ivory Coast | 25.0°C | 93% | 25.5°C | Below caution level |
| Nigeria | 25.0°C | 93% | 25.5°C | Below caution level |
| Sri Lanka | 24.7°C | 97% | 25.2°C | Below caution level |
| DR Congo | 24.7°C | 90% | 25.1°C | Below caution level |
| Qatar | 25.2°C | 45% | 25.1°C | Below caution level |
| Malaysia | 24.5°C | 94% | 25.0°C | Below caution level |
| Laos | 24.5°C | 90% | 24.9°C | Below caution level |
| Vietnam | 24.3°C | 98% | 24.8°C | Below caution level |
| Mozambique | 24.2°C | 83% | 24.5°C | Below caution level |
| Myanmar | 23.8°C | 100% | 24.3°C | Below caution level |
| Peru | 24.0°C | 77% | 24.2°C | Below caution level |
| Brazil | 23.8°C | 70% | 23.9°C | Below caution level |
| Cameroon | 23.1°C | 92% | 23.5°C | Below caution level |
| Taiwan | 22.8°C | 81% | 23.0°C | Below caution level |
| Zambia | 23.3°C | 29% | 22.9°C | Below caution level |
| Saudi Arabia | 23.2°C | 31% | 22.8°C | Below caution level |
| Uganda | 21.6°C | 86% | 21.8°C | Below caution level |
| Egypt | 21.5°C | 80% | 21.6°C | Below caution level |
| Tanzania | 21.0°C | 84% | 21.2°C | Below caution level |
| Zimbabwe | 21.2°C | 44% | 20.9°C | Below caution level |
| Iraq | 20.0°C | 72% | 20.0°C | Below caution level |
| South Africa | 19.3°C | 85% | 19.4°C | Below caution level |
| Argentina | 18.4°C | 92% | 18.5°C | Below caution level |
| Algeria | 18.5°C | 52% | 18.1°C | Below caution level |
| Morocco | 17.9°C | 88% | 18.0°C | Below caution level |
| Australia | 18.0°C | 67% | 17.8°C | Below caution level |
| India | 17.5°C | 93% | 17.6°C | Below caution level |
| Kenya | 17.5°C | 85% | 17.5°C | Below caution level |
| New Zealand | 17.6°C | 74% | 17.5°C | Below caution level |
| United States | 17.4°C | 69% | 17.2°C | Below caution level |
| Rwanda | 17.0°C | 91% | 17.1°C | Below caution level |
| Tunisia | 16.0°C | 78% | 15.8°C | Below caution level |
| Portugal | 15.5°C | 50% | 15.0°C | Below caution level |
| Israel | 14.9°C | 86% | 14.8°C | Below caution level |
| Jordan | 14.9°C | 80% | 14.7°C | Below caution level |
| Colombia | 14.5°C | 71% | 14.2°C | Below caution level |
| Nepal | 13.9°C | 100% | 13.9°C | Below caution level |
| Chile | 13.8°C | 84% | 13.6°C | Below caution level |
| Canada | 13.6°C | 93% | 13.5°C | Below caution level |
| Uzbekistan | 13.8°C | 72% | 13.5°C | Below caution level |
| Italy | 12.8°C | 84% | 12.6°C | Below caution level |
| Pakistan | 12.8°C | 81% | 12.5°C | Below caution level |
| Japan | 13.0°C | 64% | 12.5°C | Below caution level |
| Turkey | 11.0°C | 94% | 10.8°C | Below caution level |
| Ireland | 11.3°C | 64% | 10.7°C | Below caution level |
| Ethiopia | 11.3°C | 53% | 10.6°C | Below caution level |
| Iran | 10.8°C | 68% | 10.3°C | Below caution level |
| Bhutan | 9.9°C | 62% | 9.2°C | Below caution level |
| United Kingdom | 9.2°C | 90% | 8.9°C | Below caution level |
| Afghanistan | 8.2°C | 65% | 7.5°C | Below caution level |
| South Korea | 7.4°C | 94% | 7.0°C | Below caution level |
| Netherlands | 7.3°C | 80% | 6.7°C | Below caution level |
| Poland | 6.7°C | 96% | 6.3°C | Below caution level |
| Germany | 6.4°C | 96% | 6.0°C | Below caution level |
| Austria | 6.3°C | 74% | 5.6°C | Below caution level |
| Ukraine | 6.1°C | 83% | 5.5°C | Below caution level |
| Spain | 6.3°C | 60% | 5.4°C | Below caution level |
| France | 5.9°C | 68% | 5.1°C | Below caution level |
| Czechia | 5.2°C | 73% | 4.4°C | Below caution level |
| Belgium | 4.7°C | 73% | 3.9°C | Below caution level |
| Sweden | 4.2°C | 94% | 3.7°C | Below caution level |
| Russia | 2.6°C | 92% | 2.0°C | Below caution level |
| Norway | 2.4°C | 90% | 1.7°C | Below caution level |
| China | 2.2°C | 90% | 1.5°C | Below caution level |
| Finland | 1.0°C | 88% | 0.2°C | Below caution level |
How the heat index works
Sweat cools you by evaporating, and humid air slows evaporation, so muggy heat feels hotter than dry heat. The calculator uses the National Weather Service Rothfusz regression with its low- and high-humidity adjustments. It is meant for temperatures of about 27°C (80°F) and above.
In full sun it is worse
Heat index values assume shade and a light wind. Direct sunshine can add up to about 8°C (15°F). The “feels like” in many apps also includes wind and sun, so it can differ from the pure heat index shown here.
Staying safe
At “danger” levels, heat exhaustion and heat stroke become likely with prolonged activity: drink water regularly, rest in the shade and check on children, older people and outdoor workers.
Live values come from global weather models (ECMWF, ICON, GFS) via Open-Meteo and refresh every 15 minutes. All calculations on this page run in your browser.
Frequently Asked Questions
What heat index is dangerous?
The NWS calls 103–124°F (39–51°C) “danger” and 125°F (52°C) or higher “extreme danger”.
Is heat index the same as “feels like”?
Not exactly. Heat index uses temperature and humidity only; many “feels like” values also account for wind and sun.
Does the heat index apply in cool weather?
No. Below about 27°C (80°F) humidity has little effect on how warm it feels; use wind chill in the cold.