Installing a cover on your trampoline is mainly useful against dirt and leaves. The cover will keep the jumping bed clean from twig, leaves and other detritus. It is also helpful to protect the spring cover from the UV, thus increasing the life expectancy of your pad.
Installing a blanket is therefore always profitable when the trampoline is not used.
The cover will also keep the bed dry and allow the children to use the trampoline quicker after a rain shower. But it has no effect against the snow. Indeed, on a 14ft trampoline, which has a 12ft bed, we can calculate roughly 650 pounds of weight for each inch of snow. Such a load will put pressure on the mat and the springs won’t like it at all.
Concerning the wind, the only matter is that the cover must be properly tight. This prevent the wind from entering under the cover which might tear it apart or rip off the strings.
The criteria too select a good weather-cover are the quality of the PVC, the strength of the fastening system, and having a hole in the middle. This hole will allow the rain water to evacuate, thus preventing it to stagnate on the middle of the trampoline.
To select the right cover, you must simply know the size of the frame. But, in case a safety enclosure is installed, you should also check that the fitting of the cover will be possible. Some nets are fixed around the bed with strings, thus forbidding the installation of the cover.