[Selmo]

Given Tolkien's description of the geography and meteorology of the north-west of Middle Earth, it is entirely reasonable to assume that both the High Pass above Rivendell and the more southerly Redhorn Gate would be impassable in mid-winter when the Fellowship set out.

I live in England which Tolkien took as his pattern for north-west Middle Earth. I'm a few minuets drive from the southern end of a chain of hills called The Pennines. These hills are less than 3000 feet in elevation but before the developement of twentieth century machinery many routes through them would be closed for months in winter. Even now, some roads are regularly closed for days. During a particularly severe winter in the 1970s a village called Flash, just 15 miles from my home, was cut off by snow for over three weeks. It's people and their farm animals were supplied by helicopter while the road-clearing crews from three counties, assisted by the Army and the Royal Air Force, battled against the weather to clear just three miles of road. Flash is at the same latitude as the High Pass and the Misty Mountains are very much higher than the Pennines, so I have always taken for granted that the Fellowship could not cross to the East until later in the year.

I think that the fact that using the High Pass was not even considered in Rivendell means that there was more to it than just dodging a few orcs who were not under Sauron's control.
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