How Muggy works
Why not just temperature?
Because temperature doesn't tell you how the air feels. 30° in dry air is a nice day. 27° in soaked air is a slog. Your body cools itself by sweating, and sweat only cools you if it can evaporate. Wet air slows that down.
The measure of how wet the air really is: the dew point, the temperature the air would have to cool to before its moisture starts condensing. The higher it sits, the more water the air already carries and the worse your sweat works. Relative humidity can't tell you this on its own. Fog on a cold morning is 100% humidity, and nobody calls fog muggy.
So Muggy reads the dew point and sorts it into one of six bands. You see the band, not the number, because "dew point 21°" tells most people nothing and "muggy" tells them everything.
The six bands
The cut-offs are the ones WeatherSpark made familiar, converted from Fahrenheit:
| Band | Dew point | How it feels |
|---|---|---|
| dry | below 13° | Crisp. Skin and lips feel it. |
| comfortable | 13 – 16° | The good stuff. Go outside. |
| humid | 16 – 18° | Noticeable, not a problem. |
| muggy | 18 – 21° | Shirts stick. Shade helps. |
| oppressive | 21 – 24° | Sweat won't dry. Take it slow. |
| miserable | 24° and up | Stay in. Find the AC. |
What is humidex?
The band says how sticky the air is. It doesn't say how hard that stickiness is working against you: sticky air at 34° and the same sticky air at 24° are different afternoons. Humidex joins the two. It folds temperature and dew point into a single number for how heavy the air sits on a body.
Canadian meteorologists built it in 1965, and Environment Canada still issues heat warnings with it. Read it like a feels-like temperature in °C: humidex 36 means the load on you is about what 36° of dry heat would be.
| Humidex | Officially | Muggy says |
|---|---|---|
| under 30 | little discomfort | Barely registers |
| 30 – 39 | some discomfort | Fine unless you push |
| 40 – 45 | great discomfort; avoid exertion | Hard on the body |
| 45 and up | dangerous; heat stroke possible | Dangerous to exert |
This is also why evenings feel easier than afternoons when the air is just as damp: night takes away the heat, not the moisture. On the August evening this page was written, Tirana's humidex was 42 at lunchtime and 37 by nine at night. The same sticky air had become a whole level easier to be out in.
The US heat index answers the same question with different math; humidex gets the job here because it's built straight from the dew point the rest of the app already runs on. WBGT, the standard for sport and outdoor work, also measures sun and wind, but it wants instruments a weather API doesn't have. Rather than fake one, Muggy mentions the sun separately, and only when the radiation data says it matters.
"Is this normal?"
A band alone doesn't tell you whether to be surprised by it. So the app checks right now against ten years of history for the same place and time of year: every hour recorded within a week of today's date, about 3,600 of them. Then it says where this moment sits. Stickier than 93% of days, or squarely normal for here. The coloured bar underneath is the local climate at a glance, one segment per band, each sized by its share of the past decade.
"When will it get better?"
The forecast already knows when the air eases, so the app says it plainly: the first stretch in the next 24 hours that beats the band you're standing in, and where that stretch bottoms out. "Muggy from 22:00, easing to dry by 03:00." When nothing better is coming, it says that instead.
Where the data comes from
Weather and history come from Open-Meteo (CC-BY 4.0). Comfort bands follow WeatherSpark's thresholds. Humidex is Environment Canada's index. Muggy itself is open source.
One caveat worth knowing: these numbers describe a weather model's grid cell a few kilometres wide, not your street. A walled courtyard holds damp air after a seafront has cleared. Treat the bands as your neighbourhood's weather, not your balcony's.