Cumbersome I'll grant you, but heavy? They fly - they are lightweight by design.
But more importantly, why would you tote around something that can fly?
Granted, they do have limited flight times, but you don't need "down to the minute" predictions. Carry one with you on your hike, at most around 10 extra pounds for a rather large and heavy drone. When something interesting seems like it might happen, take a minute or two to launch the drone.
Even with zero warning, you can still get it set up quite rapidly, and unless it's a very short lived event, the lost time is easily compensated for by 1) being able to achieve aerial shots and 2) keeping human lives out of the reach of deadly things like expanding clouds of pyroclasm.