weather proof junction box

For a certified weatherproof enclosure, a test certificate citing the standards the enclosure complies with would be required. A third party test certificate is usually best and all major manufacturers should be able to produce these.

However, many manufacturers do not independently test their enclosures and simply quote what standards they believe their enclosures meet.

For many enclosures, other environmental factors may be more important than simply looking at the weatherproof certification.

Weatherproof does not mean water tight. Most enclosures will breathe and therefore will have moisture condense inside typically overnight.

Installation methods can also affect the life of the enclosures.
I have seen weatherproof cast iron enclosures rust away and develop holes because they were mounted on galvanised steel stands.

Hope this helps..
There are two organizations that issue construction standards for junction boxes. IEC governs internationally (except for North America, where NEMA governs).

Neither organization has a weatherproof standard. Also, the two sets of standards do not align with each other. But you might look at IEC 32 or NEMA 3R.

The IEC rating nomenclature (ab) indicates the (a) solid protection and (b) water protection. A solids rating of '3' protects against ingress of solids greater than 2.5mm while the water rating of '2' protects against dripping water at a 75-90 degree angle.

The NEMA rating of 3R protects against solid foreign objects and rain/sleet/snow from a vertical origin.