Feb is normally the coldest and best snow but it will remain all through March. We went last week of season last year (25th March - 2nd April) and skied all week. V hot and a bit slushy by the Friday. One year went in April (extended season time exclusive to Balkan) and best snow we had ever seen. You just can't tell. Whatever, weather permitting (wind etc) you can ski up in the mountains for most of the year.