Dart frogs for a beginner

[Paul Rust]

Just one instance of your frogs going to 31 °C will quite likely kill them. People kill dart frogs by getting them too cool (on the other end, 15 °C / 59 °F can cause a frog to go into decline and die slowly). You need to be able to provide temperature controlled conditions or you'll waste a lot of money on these frogs, not to mention kill the poor things.

Very good point here, just to add to it.
If they do get chilled and survive, they may never fully recover.