Growing Season: Thermal Sums

Thermal sums such as Growing Degree Days (GDD) are the cumulative degrees in Celsius above a chosen threshold temperature over a period of time. For GDD > 5, a day which averaged 15 degrees would accumulate 10 Growing Degree Days. 

The months of April and October generally mark the start and end of the growing season for winegrapes in the Okanagan. Increasing temperatures are predicted to translate to earlier harvest dates than previously observed. The following maps depict the change from the historical average of GDD > 5 in the Okanagan Valley of British Columbia, Canada.

The maps below have three tabs, each shows the same information but allows you to visualize it in a slightly different way. 

    • One the first tab (Interactive) you can zoom in and out. Importantly you can see the warming scenarios by clicking on the small square showing three layers in the upper right corner of the map; for best viewing we recommend checking only one box at a time of the three options (Historical, Moderate warming, High warming). This box also lets you change the underlying map (basic topographic or  imagery, which gives satellite views).
    • The middle tab (Compare Warming Scenarios) shows the historical, moderate warming and high warming scenarios side-by-side for easy comparison.
    • The right tab (Anomalies) shows how much of a change occurs from the recent (historical) past versus the moderate (MW) and high (HW) warming scenarios. 

More information about these maps can be found below, here. 

Growing Degree Days > 5: May through October

Growing Degree Days > 5: April through September

More Information

Anomalies are a metric which highlight the change in a variable (minimum temperature, for example) from the recent historical average (1970 – 1989). Positive values indicate a projected increase from the past. For example, a value of -2 would mean temperatures will be two degrees cooler than the historical average, while a value of 2 would be two degrees warmer than the historical average. 

Warming Scenarios:
wo warming scenarios are represented in the data. The Moderate Warming (MW) and High Warming (HW) scenarios are represented by averaging the data for the periods of years between 2040 – 2059 and 2070 – 2089, respectively. These warming scenarios represent projected future climate based on a high emissions scenario at two timepoints in the future. For more information on the climate scenarios see, About.

Average Anomalies (Warming Scenario – Historical):

    • GDD > 5:
      • May through October: the historical GDD > 5 mean is 1896, with warming the sum will rise:
        • Moderate Warming – 898 GDD
        • High Warming – 1507 GDD
      • April through September: the historical GDD > 5 mean is 1894, with warming the sum will rise:
        • Moderate Warming – 885 GDD
        • High Warming – 1483 GDD


Funding for the climate maps component of this project has been provided in part by the Canada Research Chair in Temporal Ecology and in part by the governments of Canada and British Columbia under the Canadian Agricultural Partnership, a federal-provincial-territorial initiative.
Funding is administered by the Investment Agriculture Foundation of BC. This project is part of the Farm Adaptation Innovator Program delivered by the Climate & Agriculture Initiative BC.