# Sum of temperature values with Unitful.jl
**URL:** https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714
**Category:** General Usage
**Tags:** question, unitful
**Created:** [October 7, 2023, 8:46pm UTC](https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714 "2023-10-07T20:46:20Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@fnoessler](https://discourse.julialang.org/u/fnoessler)
#### Post date: [October 7, 2023, 8:46pm UTC](https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714/1 "2023-10-07T20:46:20Z")
Hello,
is there a way to calculate the (cumulative) sum of temperature values in °C with Unitful.jl?
I know this does not have a direct physical meaning. Nonetheless, it would be nice to keep the °C unit attached to my calculated values. I want to use the yearly cumulative temperature values in an ecological system model to account for changes in growth rates of plants over the year. I think the concept is similar to growing degree days:
> **[Growing degree-day](https://en.m.wikipedia.org/wiki/Growing_degree-day)**
>
> Growing degree days (GDD), also called growing degree units (GDUs), are a heuristic tool in phenology. GDD are a measure of heat accumulation used by horticulturists, gardeners, and farmers to predict plant and animal development rates such as the date that a flower will bloom, an insect will emerge from dormancy, or a crop will reach maturity. GDD is credited to be first defined by Reaumur in 1735.
> In the absence of extreme conditions such as unseasonal drought or disease, plants grow in a cumu...
When I want to calculate the sum of °C values, I get an AffineError as expected, see:
[https://docs.sciml.ai/Unitful/stable/temperature/](https://docs.sciml.ai/Unitful/stable/temperature/)
Is there a way to overrride this behaviour and just use the temperature unit °C similiar to a length or weight unit?
Best
Felix
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### Author:  [@Dan](https://discourse.julialang.org/u/Dan)
#### Post date: [October 7, 2023, 9:51pm UTC](https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714/2 "2023-10-07T21:51:18Z")
You can use K (Kelvin) instead of C. They are the same “degrees” and K addition works.
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### Author:  [@fnoessler](https://discourse.julialang.org/u/fnoessler)
#### Post date: [October 8, 2023, 10:14am UTC](https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714/3 "2023-10-08T10:14:11Z")
thanks, maybe this is the easiest solution!
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### Author:  [@cstjean](https://discourse.julialang.org/u/cstjean)
#### Post date: [October 8, 2023, 6:37pm UTC](https://discourse.julialang.org/t/sum-of-temperature-values-with-unitful-jl/104714/4 "2023-10-08T18:37:13Z")
We follow the rule that measured (“absolute”) temperature can be in °C (or K) while temperature differences have to be in K, and it works well enough. So indeed growing degree days should be in K.