Very breathable. The solid latex pillows typically have lots of perforations for air circulation. I just got two of these pillows from Brooklyn Bedding, and I didn’t know a pillow could make me so happy:

https://brooklynbedding.com/products/talalay-latex-pillow

It feels like the perfect combination of supportive and soft. I’ve had a latex mattress for several years and absolutely love it, so I figured I’d also like a latex pillow. I haven’t tried washing them yet, but they come with an organic cotton cover that’s washable. They recommend spot cleaning the latex inserts.