Last year I picked up the Motor Trend SafeKeeper All Weather Car Cover. It’s a thick heavy duty cover that is holding up very well. It withstands rain, sun and wind & I imagine snow too. No snow here in So Cal where I live. I bought it from amazon and there a couple mixed reviews. I’ve had it for one year and there are no signs of cracking or deterioration. The price has gone up some since last year. If it lasts another year for me, which I think it definitely would, I would buy it again.
My M3 sits outside all the time and I keep it covered with the factory OEM cover, which is on its last legs. I don’t use the Motor Trend SafeKeeper all the time but when I do, I place it over the factory oem cover. That way the car & the oem cover are protected from all the elements. The Safekeeper cover has a fleece lining but the oem cover is much softer and I want to keep the softest lining against the paint. Size L – 190” fits perfectly on the car.