It is VERY cold there. It is best to buy coats there, as they have better coats for that climate. Bring a lot of warm clothing that you can layer, socks that are merino or alpaca wool, hand warmers or rechargeable heated gloves, cough syrup, fleece tights (Sisters).
There is not great medical or dental care, so get all you can done before leaving.
There is a lot of poverty.
Missionaries teach a lot of English classes. They are not allowed to proselyte, initiate conversations, or wear their tags, but they can answer questions. Despite that, the Church is growing a lot there.
There's a lot of walking in this mission, so there is heavy wear on shoes.
There are no tampons and the pads are pretty lousy, so bring feminine hygiene products. Also, Sisters report that they experience some hair loss because of the hard water. There are hair treatments that can help with this. Sisters are more likely to be in cities, but they still walk a lot as well as take buses.
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Several mommas recommended this to help with the hair loss experienced by sisters serving in Mongolia. The sisters use one or two hair treatments per transfer.