You need to increase the wing loading to make it fly better in the wind. The downside to this is the plane will fly faster and land faster.

You can do this by "clipping" the wing (remove one bay on each side) OR you can add weight to the plane.

I suggest adding some ballast to the plane and see how she flies. You didn't say what size plane and power you have or the present weight so it is difficult to suggest the amount of weight to add and whether your present engine will be OK or will you need a larger engine. As Missleman said, larger and/or heavier planes handle the wind better than lighter planes.