You should be ok, Barley is considered dry and will store at under 13% moisture (before malting). Malt is probably down in the 5% range after malting and kilning, so adding 2% by weight would still keep it under 10%. The extra moisture should just even itself out through the kernel, so you might have to add a touch more water, but I would test this first.
And if you can, keep it cool, refrigerator cool, or cold basement. Stuff will go bad faster if it is wet and warm.