Hi Sierratrekking and welcome to the forum.
Snow in October? I have just had a look at
http://www.sierra-nevada-news.com which details last years snowfall records in great detail. There was ice and some snowfall in September but the major falls didnt arrive until late-November.
That is late however and normally we would expect some snow in October. Usually better late October though. I personally have skied late October up there. Snow is likely to be soft and sporadic.
Rain records and therefore snowfall high can be found at
http://www.spanishhighs.co.uk/weather.html. This suggests there will be 3 or 4 days totally 25 to 28mm rainfall in October. Hope this helps?