Ben - I went there at the end of May last summer and it was already quite warm. But there were a few snow/ice routes in conditions at that time (N Face Col du Plan, Eperon Migot, Y Couoir on the Verte). The bigger ice faces and goulottes like Les Droites and Supercouloir were already gone or too dangerous due to the warm temperatures. It was 35 degrees in Chamonix by early June. I think if you really want to climb ice routes, either goulottes of big faces, March can be a good time. I've been there twice in March and both times, there were good ice objectives. One trip was better than the other and there were many routes to choose from. Les Droites, Les Courtes, Ravanal-Frendo, Petit Viking, Voie Charlet on Dolent, Modica-Noury, Gabarrou-Albinoni, Supercouloir, etc are often good at that time. June is too late for many of these routes. I think early May is probably a better time if you want to wait for spring/early summer. The issue at that time, though, is that the cable cars/huts are often closed. And there is often a lot of snow falling during the April/May period. In March, all the cable cars are operating for ski season. If you want, we can dicuss this by phone...e-mail me and I'll send you my number.