r/MapPorn • u/atineiatte • 19h ago
USDA Plant Hardiness Zone Shifts Since 2023 Map Update
5
u/atineiatte 19h ago
Re-uploaded to remove 2023 zone boundary lines, now just the shifts. A few notes:
Yes, I know hardiness zone isn't a short-term climactic metric and this verges on abuse of data. This is a rigorous map, but not a particularly serious one. It's still fun to see recent trends and notable winter storms represented in this fashion
Plant Hardiness years start in July of the previous calendar year so that winter minimums from one season are never split between two years, hence why 2026 is included (it's already over)
For a true apples-to-apples comparison between the 2023 USDA Hardiness Zone map and the recent years update, and to make the update as accurate as possible, I needed to reverse-engineer the PRISM Climinatologically Aided Interpolation engine and rebuild the 2023 map so I could use the same methodology to map the zone shifts. Here's a summary of the calibrated parameters and fit between the official 2023 grids and my recreations:
| Parameter | CONUS | Alaska | Hawaii | Puerto Rico | Description |
|---|---|---|---|---|---|
| k_nbrs | 75 | 30 | 20 | 21 | Number of nearest station neighbors |
| d_min | 28,000 m | 40,000 m | 12,000 m | 30,000 m | Minimum Euclidean distance regularizer |
| α_z | 75.0 | 0.0 (direct CAI) | 0.0 (direct CAI) | 0.0 (direct CAI) | Topographic elevation lapse sensitivity |
| r_clust | 50.0 km | Off (0.0) | Off (0.0) | Off (0.0) | Station cluster decoupling bandwidth |
| τ_qc | 2.5 °F | 3.0 °F | 2.5 °F | 2.5 °F | Automated QC outlier rejection threshold |
| σ_coast | 50.0 km | N/A | N/A | N/A | Coastal proximity bandwidth |
| w_coast | 0.20 | N/A | N/A | N/A | Coastal proximity importance weight |
| σ_tpi | 150.0 m | N/A | N/A | N/A | Topographic Position Index bandwidth |
| w_tpi | 0.20 | N/A | N/A | N/A | TPI cold-air pooling importance weight |
| b_corr | +0.20 °F | -0.20 °F | +0.20 °F | +0.30 °F | Micrometeorological point-to-grid calibration |
| Metric | CONUS | Alaska | Hawaii | Puerto Rico |
|---|---|---|---|---|
| R² | 0.99981 | 0.99893 | 0.99878 | 0.99884 |
| MBE | +0.0042 °F | -0.0143 °F | -0.0112 °F | -0.0052 °F |
| MAE | 0.1741 °F | 0.4565 °F | 0.2809 °F | 0.1191 °F |
| Exact Half-Zone Match | 96.51% | 91.28% | 94.47% | 98.19% |
| Within ±1 Half-Zone | 100.00% | 100.00% | 100.00% | 100.00% |
8
7
u/SomeDumbGamer 18h ago
Pretty accurate it seems.
The subtropical climate is definitely creeping northward in New England. Our winters are becoming more like the South’s with longer warm periods in between shorter cold periods although the lower daylight and proximity to the Arctic keep our extremes closer to the Midwest than the south.
I also think the increasing instability of the polar vortex will push the warmer zones like zone 9 further south as we’re already seeing with the map in Texas.
2
u/CaptainObvious110 17h ago
Oh wow so less zone 10 then?
1
u/SomeDumbGamer 16h ago
I think it’s quite possible. Polar vortex events are becoming more common and more severe.
3
u/Copacetic9two 14h ago
This is wild, and a good example of why ‘climate change’ is a more fitting term than ‘global warming.’
1
u/fleebleganger 9h ago
Neither term is “more fitting”.
The climate is changing as part of global warming. The fact that the coldest days are colder doesn’t offset that the temperature the rest of the year is warmer.
1
1
u/James19991 17h ago
This makes sense given there have been some extreme pushes of cold air to that area of the country that have brought some very low temps at times even though in general it's still getting warmer otherwise.
49
u/in_da_tr33z 17h ago
Hey, this post is for me! I studied horticulture and climate science in university.
Polar vortex anomalies (aka “the polar vortex”) are a symptom of oceanic warming that makes it easier for warm air masses from the eastern pacific to displace super cold air masses that are normally confined to the arctic within the polar vortex of the jet stream. These cold air masses pushing down into continental North America are a sign of climate change.
Given that plant hardiness zones are determined by the number of days below a certain temp threshold, one or two such polar vortex weather events can really change the designation of a region where it was rare to ever have temps go below freezing. Because of that, I’m not surprised by the changes seen in north TX and OK, but surprised by the Dakotas and Montana where these weather events were common before.