Dry season in the Occidental is supposed to be June through August with a second shorter but less windy season in Mid-December through Mid-January.
Dry season in the Oriental is supposed to be November through February (but October through January for Cayambe).
Cotopaxi can be attempted year round.
March through May is supposed to be the worst season throughout Ecuador.
At least according to all the guidebook authors, and who knows what Mother Nature will dish out.
Do you have (by any chance) any good information on weather in Northwest Argentinian Andes ?
If the Atacama region is what you are speaking about, it is pretty dry year round, but cooler in the winter. Some places are supposed to be easier to visit in winter because water is available, but summer is when most people climb most of the peaks.
Bottom line: the ash from the eruption of Tungurahua has resulted in snow melting on Chimborazo: there are "penitentes" as high as 3 meters that have made the climb difficult but not impossible. But the new thing is that the route has now got very icy...
Thanks for the info! Good to know! I guess things might change for the better or worse by the time we go. It seems that everytime I plan to climb something 20,000+ feet, something happens before we go!
Still, there are other peaks to climb if Chimbo conditions aren't good.