How do I select representative stations from 112 stations to do statistical analysis of the temp, rainfall and humidity?

I am modelling a 75000 sq km watershed with no in situ measurements for hydro-meteorological data so i depending on data sets that i downloaded from Climate Forecasting System Reanalysiswebsite. After clipping the data to my study area, i have 112 station but it is not possible for me to analyse station by station data due to time constraint. The resolution of the data is 38km.SWAT is catchment model used for rainfall runoff modelling and climate change impact studies. It isalso be used for land use change impact studies in watersheds.