Tony M Jun 2, 2015:

@ Asker It's standard EN, albeit rather unusual in this sort of context.

It simply means "unless that temperature is at least 0° and rising" — in other words, there is no danger of its going lower, and it will soon reach 3°.

It sounds as if the 3° threshold is allowing a bit of a safety margin, just to make sure it doesn't fall below 0°.

Cindy Mittelette-Longuet (asker) Jun 2, 2015:

Sauf si le thermomètre passe au-dessus de 0 °C ? Quelque chose m'échappe, je ne comprends pas pourquoi la stabilisation serait interdite en dessous de 3 ° mais autorisée si le thermomètre passe au-dessus de 0...