Temp and Humidity Chart Nov Vs Dec

Below is the Temp and Humidity chart from 15-Nov to 6-Dec. The average Temp = 28.8 degC and average Humidity = 77.7%.
During the 6-Dec visit, I had adjusted the humidity set point from 87% to 90%. Below is the temp and humidity chart from 6-Dec to 10-Jan-09. The average Temp drop to 28degC and average Humidity = 77%. The Temp is very stable now. But the humidity drop which is due to the sudden drop in humidity from 18-Dec to 25-Dec. No idea why.

If you notice that the humidity curve like saw-tooth shape. This is because the humidifier is run only from 7am to 6pm. So the humidity will slowly increase from 7am onward till 8pm and start dropping from 8pm onward till 7am. This is to make sure that birds have peace night and not to be frighten by humidifier.

Btw, there is some offset between the data logger and external humidity meter reading. When the humidity meter show 86%, the data logger reading only show 81%. So the actual humidity of my BH between 80% to 90% and temp = 28degC which is good for BH.