What humidity is good for bonsai?

I have a few bonsai like a Nana Juniper, Hinoki Golden Cypress, etc that say they like humid soil and air. It’s very dry here in Sacramento. I have seen some of my trees start to suffer under these heat waves and I believe I may be over watering them as well.

I know that I need to water them when the soil is dry to the touch, but is there any way to know what humidity is good to keep them at? We have a humidity checker that ranges from 1-4. I have tried to research online, but have come up rather empty. And most care guides just say they like humidity but nothing of how much.

Thank you in advance!

Hinoki prefer more humidity than Sacramento typically offers, but they can grow well there. The sun might be too much in some cases so you might consider sheltering the tree from afternoon sun and see how that goes. And as for the watering, hinoki like water so I wouldn’t want the tree to get more than about 50% dry between waterings. The juniper can get a little drier between waterings, maybe up to 60-70% dry. When you check for dryness on these trees, poke down 1/4-1/2" below the surface to where the roots are to measure the soil there.

Many of the species grown for bonsai prefer more humidity than they receive in Northern California, but they seem to do well despite that.

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When I recently wanted to protect a heavily pruned tree from afternoon sun I draped a white cotton shirt over it. I was surprised to feel the moist coolness of the air under the shirt after a few hours.
Is there a way you can raise the moisture level in the surrounding area when you water and perhaps tent it with a shade cloth?