Weathering a canvas tent before use is a MUST to make sure it is watertight.
Canvas tents require a pre-wetting on the first use to waterproof the tent, this
'seasoning process' also known as pre-weathering consists of soaking the whole canvas tent with your garden hose.
You will then simply let it dry completely.
By doing so, the canvas and thread will have contracted and expanded to fill the holes, interlock the fibres and provide you with a waterproof barrier.
Repeat soaking your tent then letting it dry completely at least two more times.
Now you are good to go with your watertight canvas tent!