Mars' carbon dioxide atmosphere is only 1% as dense as Earth's at sea level.
A 100 mph wind would feel like a light breeze, but would be blowing dust and sand.
Be sure to click on the "Martian air" link in the above article and read about the Kitty Hawk (!) project.
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We lived in Mountain Home AFB, Idaho when I was a kid (Air Force Brat!). That's the desert part of Idaho (southwestern Idaho). We saw dust-devils all the time there. What I remember that was such a strange thing was living across the street from the Base Golf driving range. They had water sprinklers going all the time and it was lush green. We could walk down the street about 2 blocks or so and there was a barricade at the dead end street. Beyond the barricade? Nothing but sagebrush, sand scorpion dusty desert. It was a strange thing to see such a stark contrast on base/off base.