Sounds like you are using fresh spices, like fresh grown? If so, baggies or Glad containers that seal.
If using store bought already processed spices, in either the small glass bottles or like McCormics in the metal tin??? then the glass one will seal pretty good. No problem. The metal tins? you may want to put them inside a baggie and seal it.
We leave spices in the camper all summer (until they run out), and have never had any problems with moisture or anything, closed up in their original containers. And it's not uncommon for us to take them out of the camper and bring them back into the house either.
Over the winter, when we are not prepairing meals in the camper, everything comes back into the house. We start out fresh every camping season restocking everything in the pantry. There is absolutely no food items left in the camper at the end of the season, except what we bring in and take out when we sleep in the camper on week-ends in the drive way.