The seasonal weather conditions impact strongly on the quality of a wine. In Central Otago the grape harvest occurs in Autumn (April) and is the final of the four seasons making up the annual cycle.
Winter → Spring → Summer → Autumn
In the southern hemisphere, winter (June to September) and spring (October to December) occur in the calendar year before the harvest year, and summer (January and February) and autumn (March to May) in the Vintage year. Wines from Central Otago differ from year to year with those produced in warm years markedly different from those produced in cool years. The chart below compares the monthly heat accumulation (GDD's) over seven vintages. The area under each of the lines on the chart respresents the total heat accumulation for that vintage. The greater the area the warmer the vintage. Furthermore, favourable weather during critical growth periods also influences the vintage's quality (see weather and phenology).