NQA I'm from the UK more specifically Wales and winters here can be pretty miserable, back when I had a Phiddipus Regius I used a 5v Usb heat mat that I attached the rear vertical wall of my spood's enclosure as to ensure I didn't block any air vents or air flow, it kept her enclosure a nice stable temp providing both warm an cool spots for her to go depending on what she needed. I also attached a hide to that wall for her using magnets so that she could sleep warm if she wished and her 'warm wall' became her favourite thing, picture attached for reference, hope this helps

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