You just have to check the operating specs. There are multiple issues:
Most of them won’t operate below freezing. Whether an enclosure is good enough to prevent that while still allowing signal to get through just depends on the details. There’s also an upper range on operating temperatures. Enclosures often protect from cold while increasing heat on the high end.
Electrical safety. Many jurisdictions have very specific requirements for any electrical equipment installed outdoors. Usually you can solve this with an enclosure rated to code, so again it’s a question of whether the signal can get through.
But the problem is typically solveable, as for pool monitors.
I would talk to a local electrician who installs irrigation or pool equipment to see what your local jurisdiction might require.
Also, be aware that there is significant signal loss during rain. Whether it’s in an enclosure or not, it’s the distance the signal has to travel from the antenna to the next receiver device. For this reason many manufacturers advise against putting disaster monitoring equipment outdoors, as the signal might be lost in exactly the kind of weather likely to cause the condition being monitored. This is probably the biggest issue. Even if you do decide to put the valve itself outdoors, I’d be tempted to bring the transmitting antenna itself inside, or at least to the wall’s edge.