When to Plant Tomato in Zone 4
As of 2026-09-11, USDA Zone 4 (USDA Plant Hardiness Zone Map) has an average annual winter minimum of -30°F to -20°F. PlantingWindowPlan's Tomato thresholds preset for tomato treats a day as a planting candidate only once measured soil reaches 60°F and the forecast overnight low stays at or above 50°F.
- Crop
- Tomato
- USDA zone
- Zone 4
- Zone winter minimum
- -30°F to -20°F
- Preset used
- Tomato thresholds
- Minimum soil temperature
- 60°F
- Minimum overnight air
- 50°F
- Maximum daytime air
- 90°F
What zone 4 means for tomato
Zone 4 is typical of central Minnesota, Wisconsin, Maine, and the northern Great Plains, and describes average winter cold, not a specific last-frost calendar date. Areas in this zone generally have a short to moderate frost-free growing season, but the exact last-frost date varies by city, elevation and year. Tomato is a warm-season crop that this app’s Tomato preset assumes is planted after the soil and overnight-air thresholds pass.
To turn this into a real date: open the tool, use the ZIP-based zone lookup to confirm your exact zone, then import the live forecast for your city and enter a measured soil temperature. The candidate day is the first forecast day that passes every threshold above, not a fixed date on a calendar.
Frequently asked questions
What USDA zone am I in?
Zone 4 covers areas with an average annual winter minimum temperature between -30°F and -20°F, per the USDA Plant Hardiness Zone Map. Use the tool's ZIP-based zone lookup for your exact zone; national zone bands do not replace a local reading.
Does zone 4 tell me the exact planting date?
No. Hardiness zone describes winter cold, not a specific last-frost date. Use the tool's live weather import for your location, plus your own soil measurement, to set the actual candidate day.
What thresholds does this page use for tomato?
The Tomato thresholds preset: minimum soil 60°F, minimum overnight air 50°F, maximum daytime air 90°F. These are editable starting assumptions, not a universal rule.