Your weather app is honest. It is just answering a different question than the one you have. It tells you what the day is like for someone walking to work, not what it is like for someone running six miles. Learn to read four numbers the way a runner should, and you will be dressed right far more often than the forecast headline would get you.
Feels-like, not the temperature
The air temperature is the least useful number on the screen. The feels-like temperature is better, because it already folds in wind chill in the cold and the heat index in the warmth. That is closer to what your skin actually experiences, and it is where you should start every clothing decision. Then remember that running itself adds heat on top, which is the job RunFeel does.
Wind: the most underrated number
Runners routinely ignore wind, and it is often the number that decides whether a run is pleasant or punishing. A 45-degree day at 20 mph feels more like the mid-30s, and dressing for the calm temperature leaves you cold in the headwind sections.
Two habits fix it. First, treat wind as a reason for a thin shell and ear coverage, not an afterthought. Second, plan the route so the headwind comes early, while you are fresh and dry, and the tailwind carries you home.
Dew point over humidity
Relative humidity is a percentage that shifts with temperature, so it is hard to compare day to day. The dew point is an absolute number, and it tells you directly how muggy it will feel and whether your sweat can cool you. A high dew point is what turns a mild-looking morning into a hard hot run. When it climbs into the 60s and 70s, slow down and judge the run by effort.
UV and air quality
Two numbers that have nothing to do with how warm you feel but plenty to do with your health. UV peaks in the hours around midday and is the reason for a cap and sunglasses on clear days, regardless of temperature. Air quality shifts hour to hour and can turn an otherwise perfect run into one worth rescheduling, especially for anyone with sensitive lungs.
Put it together
No single number tells the whole story, which is the point. The feels-like, the wind, the dew point, and the UV and air quality combine into the real character of a run, and they combine differently every hour. That is why the smart move is not to read one forecast but to compare the hours and run the best one. RunnersKit does that for you: it rolls these inputs into RunFeel, scores every hour, and tells you when your window opens. The full method is laid out on the how it works page.