Formula used
Last spring frost: percentile of historical spring dates at 1 − risk.
First autumn frost: percentile of historical autumn dates at risk.
Frost-free days: autumn frost day minus spring frost day.
Safe planting: spring estimate plus crop tolerance and safety days.
How to use
- Enter a location and choose its climate profile.
- Select a frost threshold and acceptable risk level.
- Choose a crop, protection method, and safety buffer.
- Add historical records for location-specific statistical results.
- Calculate, review charts, then export the summary.
Example data
| Setting | Example | Purpose |
|---|---|---|
| Climate profile | Temperate inland | Provides a planning baseline. |
| Frost risk | 20% | Balances safety and season length. |
| Crop | Tomato | Creates transplant and harvest dates. |
| Protection | Row cover | Extends usable growing conditions. |
Frequently asked questions
What is a last spring frost date?
It estimates the season's final damaging cold event. Later frost can still occur. Always check local forecasts before planting tender crops.
What is a first autumn frost date?
It estimates when freezing temperatures may return. Early frost can shorten harvests. Protective covers may extend the useful growing season.
Which risk percentage should I choose?
Lower percentages create more conservative planting dates. Tender plants benefit from lower risk. Hardy crops can tolerate greater planning risk.
What does the frost threshold change?
It defines the cold level being analysed. Hard frost dates usually differ. Select thresholds matching your crop's sensitivity.
Can nearby gardens have different dates?
Yes, microclimates can change local temperatures significantly. Valleys often collect cold air. Urban sites may remain warmer overnight.
How does elevation affect frost?
Higher sites often cool sooner and warm later. Terrain modifies that pattern. Use manual offsets for known local behaviour.
Should I use manual historical records?
Use them when reliable local observations exist. More years improve stability. Remove records containing obvious measurement errors.
Does a greenhouse eliminate frost risk?
No, unheated structures can still freeze. Protection effectiveness varies widely. Monitor internal temperatures during cold nights.
Is this a live weather forecast?
No, it provides historical planning estimates only. Weather changes remain unpredictable. Confirm decisions using current local forecasts.