Weather station , which one to use

All those fancy weather stations are just as accurate as an aircraft altimiter and this temp/humidity gauge. This one is what I use and it is certified.

http://www.professionalequipment.com/xq/ASP/ProductID.1091/id.22/subID.322/qx/default.htm

 

You set the altimeter at 29.92 and read the altitude directly. You need density altitude software that will accept altimeter inputs like Davenports Jetsize or Density. They all use 29.92 as a standard. If the software will not accept altimeter readings then one will need a barometer but it has to be calibrated to read raw (actual) pressure vice corrected pressure (at sea level) or you are always going to be dependent on knowing the correct track altitude. I take my barometer to the weather office at the Air Force base and have them read me the raw (actual) barometric pressure and I calibrate the instrument.