They wipe right off with a wet towel, but stand up in the rain:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

5mm Medium Tip Erasable Liquid Chalk Markers (33 Pens Size M) w/ 45 Chalkboard Labels, Wet Erase For Nonporous Surfaces - All Bright Neon, Metallic, Macaron & Classic Colors, Reverse Bullet Chisel Nib
https://www.amazon.com/Erasable-Chalkboard-Metallic-Reversible-Splinter/dp/B07S32MD7F

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Boley Spray Chalk Paint - 8 Pk 200 gram Washable Sidewalk Chalk Spray Paint Cans for Kids Ages 8+

Available on Amazon Now