As long as they can get shade and water during the summer they should be juussstttt fine. We keep our waterers in the shade too so it doesn't get up to near boiling temperatures in August. XD
Occasional ice treats will help on the really high temp days too while keeping them entertained..... a double win.
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Mixing various LF breeds with similar climate tolerances is usually fine. The RIRs and Dominiques should be just fine together.
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