Currently the latest `proplot` version only supports `matplotlib<=3.4.3`. Given that `matplotlib` is up to 3.8.3 and the latest `xarray` versions require higher versions, we should push to support the latest `matplotlib` here. It could be fruitful in the future to run a nightly test suite running the bleeding edge of this repo against the latest `matplotlib` version to detect this sooner. The conda feedstock is also locked at `matplotlib-base < 3.5.0` due to these issues. See PR here waiting for new proplot release: https://github.com/conda-forge/proplot-feedstock/pull/28.