Its one of the top five projects that all amateurs want to make. The educ8s team (This is SPARTA) uploaded a step by step guide on how to make an inexpensive weather station with the DTH11 humidity sensor and the BMP180 barometric pressure and temperature sensor. The project is based on the Arduino board and uses a 16 by 2 LCD to display the results. Its quite precise as far as the pressure and the temperature is concerned. It could use a better (and more expensive) humidity sensor though. Nevertheless, its a very good starting point!