I think it is weather sealed over being "water resistant", but yes, if you use a non sealed lenses, you might have trouble. Although, a lot of people have been shooting non-weather sealed cameras and lenses in the rain and snow. I think it's where you will be shooting, weather-wise and how you decided to safeguard it!
If you're chasing storms, I wouldn't recommend it despite it being weather-sealed. However, I will happily shoot a non-sealed camera under an umbrella, in a car with open window under heavy rain!
So ultimately I think having weather sealed camera, means if you're shooting on the streets and you get splashed with water of shooting in lighter rain, your camera will not likely to suffer without protection. I wouldn't submerge your camera and lens.