I’ve seen people sharing Growing Degree Day (GDD) calculators in various topics here and thought it would be helpful to compile them all in one place. Some give more detail than others, but they are all useful. If you don’t know, GDD is an approximation of how much heat your plants receive in the growing season. With some caveats, all else being equal, more heat = more growth or fruit ripening. Knowing your average GDD can be helpful for determining if a fruit or nut will grow well for you.
If anyone else knows of a good one I missed, feel free to add it. Also please chime in with a more thorough discussion of GDD.
Note: All the resources I know of focus on the contiguous US. I’d really love if anyone could point me to similar resources for other regions of the world.
Northeast GDD calculator: Climate Smart Farming CSF Growing Degree Day Calculator
Southeast: Growing Degree Days Calculator – AgroClimate
Cooling degree days (same idea from another direction, intended for estimating AC energy use): http://www.weatherdatadepot.com/ (thanks @Barkslip)
I’ve seen reference to minimum cooling degree days for pecans, so I included this one as well.
If you’d like to quickly compare between regions, here is a web map of average annual base 50 GDD (30 year) that I made using data from the National Phenology Network. I wasn’t able to make it as detailed as I would like due to limitations of the free version of ArcGIS Online. I divided the country into 500 GDD sections, but I was only able to get 10 categories for color, so it is colored in 1000 GDD increments. You can search for your address and click on the map to see the minimum GDD for that zone. If you’re close to the line of the next zone up, you can presume you’re closer to the high end of your zone.
Another good source (but slightly harder to use) is the National Phenology Network data visualization tool. It takes some getting used to, but you can access information such as first bloom times for common species, GDD, and more. I personally like the gridded layers.
Here’s the formula/rules to calculate your own GDD if you have the data: https://ndawn.ndsu.nodak.edu/help-corn-growing-degree-days.html