Sometimes people complain that their measurements don’t match the expected measurements. I think that is only good, because if it always did, you didn’t need a weather station in the first place. If it always doesn’t, you might need a calibration, if after the calibration it always does, back to step one, you don’t need a weather station. Actually for something like barometric pressure, you probably don’t need a weather station, it is varying very slowly over distance so you might look it up at some other station.
You only need a weather station for parameters that do have a strong local dependency (or you need one to drive your home-automation, which is a different ball game).
Some parameters like for example UV and rain, don’t depend too strongly on where you put the device near your house, as long as it isn’t in an obvious bad spot (like under a roof). UV/sunshine is easy, just put it in a sunny spot, which the unit needs to be anyway, as it is using solar energy to power itself. Rain is very sensitive to how you mount it. Vibration free is key here. (a bit of swaying in the wind could be ok, but that might influence the wind measurements).
Temperature is pretty easy to get near what you expect (but expect higher temps on a black roof in summer). But if you want it mostly for gardening, I wouldn’t put the unit on top of the house. Humidity is probably also more interesting for gardening (unless you want to predict when it might start raining based on dew-point measurements).
Wind is a bit hard as this is probably the most local thing. Personally I like to know the direction and speed for when I’m cycling outside the city. Therefore I’ve put it high on top of my house. I thought I was clever and tried to film the turbulence using the light snow we had lately. But unfortunately white snow on a background of white clouds makes this very hard to do ;-). (using a bright lamp at night might work better)
Having said all this, it might look as if I don’t care about exact measurements. That isn’t true. I do want to have precise and accurate measurements, but they should measure the values in my location and environment. I do accept that some measurements, such as rainfall aren’t as accurate as I would like, but then again I love the technology. It’s just amazing that they can get some useful results by basically just listening to the rain.