Moisture in organic forest floor material for boreal ecosystems plays on important role in fire behavior. Therefore, data from in situ moisture sensors were compared with sampled moisture data and weather information to assess moisture dynamics in feather mosses (Hylocomium spp. and Pleurozium spp.) and associated duff on the forest floor on boreal Alaska. Time-domain reflectometers (TDRs) illustrated moisture variability at spatial and temporal scales that are useful in predicting fire severity. For example, Hylcomium moss tended to dry at a more rapid rate then Pleurozium, the near-surface moisture condition was more spatially variable in the early season then in mid- to late season, and re-wetting of dry moss required greater changes in precipitation and relative humidity than further wetting of damp moss.