What is the lowest temp in which an oleander can survive? We had them in California, so I know their heat tolerance is amazing. But, where I live in Colorado, on rare occasions, we reach below zero.

AutismMom to NGA
Sorry, they probably won't do well... Oleanders (Nerium oleander)

edited to add...Taken from database... Minimum cold hardiness: Zone 9b -3.9 °C (25 °F) to -1.1 °C (30 °F)

I have one here in Zone 4 but it's in a pot that we bring into the basement for the winter. We've had it for many years. I think it will survive -5C (23F) but may be damaged at that temperature. That's my cut off temp for bringing it indoors. I'd expect much lower than that to be fatal. It is very easy to overwinter in the basement, if you have one. We keep it on the dry side. Dubious as a houseplant given its toxicity.

We've had them for years and they have survived in our yard down to 22 F.