Planning reference

Soil Temperature vs Air Temperature

Use measured soil warmth for germination and root-zone readiness, then use air temperature, night lows, frost risk, and cover ventilation for plant-out timing.

Planning reference

Soil Temperature vs Air Temperature cockpit

Use soil temperature for seed and root readiness, then use air temperature for injury risk, transplant stress, and cover ventilation. Warm air alone is the weak signal.

Warm afternoon air does not prove the seedbed or root zone is ready.
  1. 1 Soil temperature Measured seedbed warmth controls germination and early roots.
  2. 2 Air temperature Night lows, wind, frost risk, and sun exposure control plant-out stress.
  3. 3 Planting action Direct seed from the bed reading; transplant from roots, hardening, and forecast.
Soil reading
50Fdefault measured seedbed
Ready crops
33catalog entries ready at 50F
Wait list
70catalog entries waiting for warmer soil
Last frost
Apr 15spring cold-risk edge

What each signal answers

Soil temperature
Soil temperature is the measured warmth in the seedbed or root zone. It controls germination speed, early root growth, and whether direct-sown seed can emerge cleanly.
Air temperature
Air temperature is the daytime and nighttime weather around the plant. It controls frost injury, transplant shock, wind exposure, cover ventilation, and warm-season crop stress.
Germination readiness
Germination readiness starts with measured soil warmth, sowing depth, seedbed moisture, and crop tolerance; a warm afternoon does not mean a cold bed is ready.
Transplant weather
Transplant weather means night lows, wind, sun, hardening-off, and root-zone warmth all fit the crop before seedlings leave protected trays.
Season-extension trap
Season-extension trap means covers can warm soil and air early, but they can also overheat plants, block pollinators, or hide dry beds if they are not vented and removed on time.

Planting workflow

Measure the bed, not the mood
Do not move warm-season crops outside just because the afternoon air feels warm; check measured soil temperature, night lows, frost risk, crop tolerance, and cover ventilation before changing the planting plan.
Use soil first for seed
Before direct sowing, compare the 8 a.m. soil reading with crop germination ranges, then check depth, crusting risk, and steady seedbed moisture.
Use air and soil for transplants
Before transplanting, check hardening-off, night lows, wind, water, frost risk, and warm enough roots so seedlings do not stall after plant-out.
Separate cool and warm crops
Cool-season crops may tolerate cool soil and light frost, while warm-season crops usually need frost-free air plus warmer soil.
Treat covers as temporary tools
Use row covers, hot caps, or low tunnels to buffer early conditions, then vent, water, scout, and remove them when heat, height, or pollination becomes the bigger constraint.

Use these paths

Source basis