The Barolo zone is located southwest of the Barbaresco zone with only the vineyards of Diano d'Alba planted with Dolcetto between the two nebbiolo strongholds. Compared to the Barbaresco zone, the Barolo zone is cooler and located on higher elevations, rising nearly above Barbaresco. The harvest of the late ripening nebbiolo grape usually takes place in early to mid-October though some producers are experimenting with viticultural techniques that allow for an earlier harvest in late September. At harvest time, rains and downy mildew are two of the main hazards to worry about, along with early spring hail damage earlier in the growing season. Like most of south central and southeastern Piedmont, the zone experiences a continental climate tempered by the Tanaro river and its tributaries - the Tallòria dell'Annunziata and Tallòria di Castiglione - that split the region into three main zones. To the west of the Tallòria dell'Annunziata is the commune of Barolo and La Morra. To the east of the Tallòria di Castiglione is the commune of Serralunga d'Alba located on one of the highest hilltops in the Barolo zone. Separated by a narrow valley to the west is the commune Monforte d'Alba located in the Monforte hills. Further upstream north, located in the v-shape spur between the two tributaries is the commune of Castiglione Falletto.