Personally I wouldn't worry, I only bring mine back in if it's going to get below freezing and that is only because they can't dig down deep in the soil outside, because my pens have wood bottoms.
lows of 38 or anything above 32 for that matter and mine stay outside, but thats just how I look at it, 38 at night they will just burrow into the substrate and reamin inactive untill it warms up.
Jeff
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You got your regius's to the wall, man!
1.0 pastel Python regius
0.1 mojave Python regius
0.1 normal Python regius
0.2 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.1 Ambystoma tigrinum
1.1 Thamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
1.1 Iowa snow Thamnophis radix
1.1 heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus