hope-,
They call them casement windows. I'd do an inspection on the outside and see if you need to re-caulk the outside. That could be part of the cause for water intrusion.

regards, rredogg

Sometimes you can sand the water marks off if they're not too severe. I've had success using bleach diluted with water. Paint it on the spots and let it sit. Keep it wet. It works pretty well within 15-30 minutes. Rinse it off with a wet rag and let dry, then sand.

You may want to re-varnish with an exterior poly like Zar. The interior/exterior varnishes don't seem to withstand the moisture and UV rays like the purely exterior varnishes do.