How the frost model works, and how far off it is.
Nothing here asks for your trust. The numbers are measured on stations held out of training, and the method is open.
How prediction works
TabPFN, an open tabular model, is trained once on 6,784 NOAA weather stations. It learns the last-spring and first-fall 32F frost dates from latitude, longitude and elevation. We run it offline across a 0.5-degree US grid of 4,069 points and ship the result, so no model runs when you ask for a plan.
Accuracy
Measured on 1,357 held-out stations. Error is the average miss in days, lower is better.
TabPFN beats the nearest-station baseline on both targets. RMSE runs higher (18.2 and 32.5 days) because a few percent of stations near the frost-free south have a freeze date that straddles the new year, where a single miss counts for a lot. Those areas are labelled rather than given a hard date.
Data sources
| Input | Source | Terms |
|---|---|---|
| Frost dates | NOAA NCEI U.S. Climate Normals 1991-2020 | Public domain via NOAA NODD, attribution requested. DOI 10.25921/4ek7-fk11 |
| Frost model | TabPFN v2 (Prior Labs) | Code Apache-2.0, weights Prior Labs License v1.1. Built with PriorLabs-TabPFN |
| Advice prose | Gemma (open weights) | Gemma Terms of Use, the output is ours to use |
| Crop timing | US extension and USDA guidance | Facts, compiled into our own dataset |
What is real and what is simulated
| Piece | Status |
|---|---|
| Frost dates | Real TabPFN predictions from NOAA normals, baked offline. The error is the figure above. |
| Sow-this-week plan | Real. A deterministic function of your frost dates and today. |
| Advice prose | Written by Gemma when a key is set, else the built-in planner. The plan labels which wrote it. |
| Deep-south frost-free areas | Labelled, not given a hard date, since the model extrapolates poorly where stations rarely freeze. |
Written by Gemma
Real output from gemma3:4b running locally, for sample locations. In the live app this same engine runs when a key is set, with the built-in planner as the fallback. How to turn it on.
It’s a good time to get your garlic planted now. You should sow your spinach this week as it’s frost-hardy and grows quickly. Radishes are a great choice too as they’ll be ready before the first frost. Peas can wait until February 20th when the window opens.
You can sow spinach and radish this week as they are cold tolerant and can overwinter under cover. There are six days until the first fall frost on October 16th so you should finish your radish plantings quickly. Garlic can be planted when the window opens around October 25th. Remember that the last spring frost was on May 10th and you have 212 days until that date.
It’s a great time to plant in Phoenix this week. You can sow lettuce carrots peas and spinach now for a good harvest. The first fall frost is December 15 and there are 66 days until that date. You should hold off on planting tomatoes until around February 15.