What Is the Heat Index?
The heat index (or apparent temperature) shows what the temperature feels like when humidity is factored in. At 33°C with 70% humidity, the heat index can reach 41°C — well into the danger zone.
Why It Matters
Your body cools itself by sweating. When humidity is high, sweat cannot evaporate efficiently, and your core temperature rises. The heat index captures this effect.
Heat Index Danger Scale
| Heat Index | Risk Level | Symptoms |
|---|---|---|
| 27-32°C | Caution | Fatigue possible with prolonged exposure |
| 33-39°C | Extreme Caution | Heat cramps, exhaustion possible |
| 40-51°C | Danger | Heat exhaustion likely, heat stroke possible |
| Above 51°C | Extreme Danger | Heat stroke highly likely |
Heat Index Table
| Temp \ Humidity | 40% | 50% | 60% | 70% | 80% |
|---|---|---|---|---|---|
| 27°C | 27°C | 27°C | 28°C | 29°C | 30°C |
| 30°C | 30°C | 31°C | 33°C | 35°C | 38°C |
| 33°C | 34°C | 36°C | 38°C | 42°C | 48°C |
| 36°C | 39°C | 42°C | 47°C | 54°C | — |
Staying Safe
- Hydrate before you feel thirsty — thirst means you are already dehydrated
- Take breaks in shade or air conditioning every 30 minutes
- Wear light, loose, light-coloured clothing
- Check on elderly neighbours and pets
- Never leave children or animals in parked cars
Check the feels-like temperature on Weather Tomorrow.
Get tomorrow's forecast in your inbox
Free daily weather email. Choose your city, pick your time.
Subscribe — FreeRelated Articles
Running in Different Weather — A Complete Guide
Rain, heat, cold, wind — each weather condition changes your run. Here is how to adapt your pace, gear, and strategy.
Planning Outdoor Events Around Weather — A Practical Guide
Concerts, festivals, markets, and sports events all depend on weather. Here is how to plan smart and handle the unexpected.
Outdoor Wedding Weather Planning — The Complete Guide
Your outdoor wedding depends on weather. Here is how to plan for it, monitor it, and prepare backup options.