Well, here is a response from Brent :

"Hi Dmitry,

You will have no worries, the speakers are subjected to great variances of temperature and humidity without problems. The cabinets are very dense while the drivers due to there composition resist the elements, Ian
actually leaves his outside year round within a sheltered boathouse.Do keep the M60Ti on your scope, you will be glad you did."

Much "rejoicing in the land" is to follow .

Regards,
Dmitry.