We used a painter's tarp for years. Very lightweight, and it did keep the tent very clean. We actually like the way an oversized groundcloth can provide a kind of "porch" for the tent. Makes it easier to get in and out of the tent without tracking in dirt and debris.

Of course if it rains, you need to pull it in underneath the vestibule, or it just collects rainwater....
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Or just read a good mystery novel set in the Sierra; https://www.amazon.com/Danger-Falling-Rocks-Paul-Wagner/dp/0984884963