99% humidity during the night and indoors using DHT22

Question

I've been playing with the DHT22, but the humidity values are very intriguing.

During the night or indoors the sensor is returning 99%. While the temperature values looks good.

Here is a visualization for the last 12 hours:

Before 10:30 the sensor was indoor, I put it out to test if I still have the same values. The sensor is fully exposed to the sun after 10:30.

I'm using the Adafruit DHT python library to fetch the values:

import Adafruit_DHT as dht
import time


def get_data(sensor, pin):
    h, t = dht.read_retry(sensor, pin)
    return h, t


def main_loop():
    while True:
        h,t = get_data(dht.DHT22, 4)
        payload = {
            'temperature': round(t, 2),
            'humidity': round(h, 1),
            'timestamp': int(time.time() * 1000)}
        print payload
        time.sleep(60)



if __name__ == '__main__':
    main_loop()

As you can see, the sensor is plugged in the GPIO#4 of the RPi3.

I don't know if this is a problem, if the sensor is broken, but 99% humidity is very excessive.

Since I don't have anything else to verify these values, how can I understand the problem and fix it ?