Why are the humidity readings different?

Question

Arduino

I noticed this thing for a long time: on all sites with a weather forecast and current weather readings (I looked at a lot of different sites), they write about humidity, let's say that it is 87% (specifically in my city, now it is), but at the same time that purchased weather stations that the sensors (I currently have a BME280) show humidity around 20-25%.
Can someone explain to me how this works? And who to believe?
PS I live in the bay and the humidity of 87% seems to me closer to the real one.

Answer 1

1. Humidity floats well geographically
2. Humidity can be given by calculation, or by sensors.
3. Some forecasts show the weather on the moon (average weather for the region) and do not take into account your local conditions.
4. Who would calibrate all these local weather stations to the same standard.
5. Local weather stations can lie from direct sunlight.
6. Version: Station - cheap guano, poor quality.

Answer 2

I hope that with your sensors you measure the humidity on the street, and not in the apartment?
The fact that Chinese humidity sensors are, to put it mildly, a lottery has long been known. In purchased "weather stations" most likely they are also used.
Here, as in any measurement, you need a standard. You need some kind of certified hygrometer by which you will check all your sensors and choose the most suitable one. And the rest - no luck!

Answer 3

The first thing that suggests itself is different humidity (relative, absolute, specific, temperature)