Read Humidity and Temperature on PC
A High humidity like 90% is seen after a Rainfall, A low Humidity like 25% means dry days. A humidity of around 50% is healthy, above that Bugs and Fungus trouble. Less that 40% cause skin and breathing irritations. 60% is comfortable for us and most equipment. High humidity can cause trouble to unprotected electronics.

This device has a serial interface, that means you could use a Serial to USB circuit and even interface with your Android tablet.
"This is an assembled unit which interfaces with a PC COM port and provides the capability of measuring the relative humidity and temperature using a Sensirion SHT-71 sensor. It includes an assembled printed circuit board, a 12 VDC wall power unit, and a six foot serial cable (DB9) . The unit interfaces with a COM port or similar at 9600 baud. (A USB to RS232 converter may be used)."
SHT71 - Digital Humidity and Temperature Sensor
Replaceable relative humidity sensor, The internal calibration allows for simple and easy replacement in demanding environments. The capacitive humidity sensor SHT71 is fully calibrated and provides a digital output.