Display more than one attribute in symbology in ArcGIS Pro?

Something like this would work by using Multiple Attributes, unsure if this is still available in ArcPro? https://support.esri.com/en/technical-article/000010616

Please let me know if I'm understanding your questions correctly: so you want to display values of MULTIPLE fields in the symbology?

If so, what I'd do is to use Unique Values as the Primary symbology method. And just add the field that you want to include, which will be temp and p in your case.

If you use the Dot Density method for your symbology, you can create custom expressions based on your attributes:

This seems to be easier if you break up your continuous variables into categorical brackets, since you can set a unique color and dot density for each bracket. If this is difficult to do in the custom dialogue box (the green X), try creating a new field with an ID for each temperature-precipitation combination bracket and using that for your custom expression:

(Note: I made this with a shapefile I had on hand. Yours may look different.) Unfortunately, if you have a lot of categories, you'll have to set them one by one: $feature.Id == 1, $feature.Id == 2, etc.

Add the layer a second time; turn all the symbology to colorless. Label both layers, one per attribute.