Most modern WX radars talk about 5m safety distance.
It might not be very dangerous but the energy emitted by the system is still far higher than any other source like communications (handphone, satellite, WLAN etc). So as long as we are not sure if these sources are dangerous, I would be somewhat cautious and don't use it beyond the manufactor limitation.
It is widely accepted that one only uses it in the air or lined up on a runway, sometimes already on taxiways when pointing away from ground handling personel.
Biggest misconception about radar emissions is that their radio waves are different to those "unhealthy" ones, like the radio activity (alpha, gamma particles). The later can be summed in your body and finally lead to cell destruction. Radio waves from radio emitters are different: They only are harmful if you get too much per time unit. They don't sum up in your body. You can compare it with your microwave oven: If you sit in front of it, your dosis is minimal, if you're inside, your body gets boiled.
Dani