Bordeaux vignerons are by turns delighted and worried by the extraordinary mini heatwave that sat over Bordeaux last week. As most of Western Europe basked in weather more common in June than April, Bordeaux sweltered in temperatures that regularly topped 30 degrees Centigrade.But winemakers now have another cause for concern: that the sun is bringing the vines on too fast, leaving new buds vulnerable to April frost. Every visitor to Bordeaux last week remarked on the transformation of the vines from bare forks at the beginning of the week to substantial leaf growth at the end.