In reply to Hammy78: Varies all the time. What route / routes are you thinking of? Do you mean ground and / or weather conditions? Weather can be more stable beginning of September compared to early August. The Tacul slope can have gaping / more challenging bergschrund as snow bridges melt. Apart from around the Tete Rousse hut the Gouter Ridge to the hut is likely to be free of snow / dry. Haven't done other MB routes at that time of year. Have fun!