The only successful low cost solution I have is drain holes and/or heaters. Nearly every properly secured water proof enclosure will eventually fill with water if installed with conduit holes anywhere but the bottom and sometimes even then water will get in the box after the conduit fills with water. This experience is from industrial environments. No matter what I do, eventually some idiot opens the enclosure looking for something unrelated to my equipment and then does not properly secure the cover. Bob N5TX