Minimum temperature for LED bulbs
It is exactly what it states. That’s the minimum temperature for the bulb to start. It doesn’t necessarily mean the bulb won’t work below that temperature. It probably will light. Rather it means either that some of the electrical components will not perform within specs below that temperature, it simply wasn’t tested below that temperature, or use below that temperature will cause damage and limit it’s lifespan. If you’re going to regularly use the bulb at -40, get one rated for that for lower temperatures. If nothing else, it will likely mean replacing the bulb less often.