[Mikko]

Having ±5% would be fine for this price class, but 10 - 30% is not. I believe that those cheap sensors are not meant to last outside for several months. I do have now a new Vantage Pro with SHT31 humidity sensor and that match quite closely to SHT11 readings, both are outside about 5 m apart. Will replace other sensors with SHT31 before winter time.
BME280 sensors will also go outside and it's interesting to see how they survive, since designed for automotive applications.