Hi Rick,
The info is sketchy with many gaps but there are a number of first hand accounts that mention climate. Of course extremes are most often mentioned, in particular the 110+ temps in July 1862 and the snow and ice in January 1863. Wiley Britton's 'Memiors of the Rebellion of the Border 1863" comes to mind. The Butler Center for Arkansas Studies has the diary of a soldier of the 9th Wisc Inf that was in the First Indian Expedition (late June to early August 1862). There is also a diary by a member of the 2nd Ohio Cav. I know there are others but I'll have to do some checking to give you precise info.

Ken