Central Otago is the country’s driest region. Some valleys receive less than 600 millimetres of rainfall a year. It is also the hottest region. This is because of the clear skies, which allow sunlight to heat the ground. Heat radiating upward heats the air even more. Relatively warm air coming from the west also warms further as it descends from the mountains. As Central Otago is the most distant region from the coast, the sea does not moderate temperatures as much as elsewhere in New Zealand.