Where SoilIQ's soil temperature readings come from, how accurate they are for your specific location, and when to trust the app versus your own thermometer. No jargon — just honest answers.
SoilIQ reads soil temperature from Open-Meteo, a free meteorological API that blends ERA5-Land satellite reanalysis data with current weather model output. ERA5-Land is produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) — the same organization that runs some of the world's most accurate forecast models. SoilIQ also cross-references soil texture data from ISRIC SoilGrids, a global soil science database maintained by the International Soil Reference and Information Centre, to fine-tune readings for your local soil type.
In plain terms: the app uses the best publicly available atmospheric and soil science data and runs it through several layers of correction to get as close as possible to what a probe in your ground would actually read.
Honestly — very good for planning, not perfect for measurement. Here's the nuance:
The seasonal pattern, the depth profile (surface vs. 6 inches vs. deeper), the response to weather events like heat waves and cold snaps, and the relative trend — warming, cooling, stable. These are what matter most for planting decisions, and they're accurate within 1–3°F for most locations under normal conditions.
Highly localized conditions: a raised bed surrounded by concrete (runs warmer), a north-facing slope with heavy shade (runs cooler), or an unusually sandy or clay-heavy soil. The model uses a regional average, not a sensor in your specific garden.
Probe Calibration: If you own a soil thermometer, SoilIQ has a built-in calibration feature. Take a reading at a specific depth, enter it in the app, and SoilIQ permanently corrects all future readings for that depth. One measurement session calibrates the app for your specific microclimate indefinitely.
Close — but not instant. The app fetches fresh data from Open-Meteo and updates as frequently as every 15 minutes when you're actively using it. On the Today tab, the temperature shown is the model's best estimate for the current hour at your location, not a delayed daily average.
The 14-day forecast uses the same model data that powers professional weather services. Accuracy decreases with lead time — days 1–5 are reliable, days 6–10 are directionally sound, and anything beyond 10 days is better used for general awareness than firm planting decisions.
No — your thermometer is more accurate for your exact spot. A probe in your actual soil, at your actual depth, on your actual property, is more accurate than any model. If the app says 58°F and your thermometer says 54°F, trust your thermometer for today's planting call.
Where SoilIQ is genuinely better than a thermometer: it tells you what's happening at multiple depths simultaneously, shows you a 14-day forecast, tracks your historical trend, and works even when you're not there — before you drive to a site, or while planning from inside the house in February. A thermometer can't do any of that.
Use them together. SoilIQ for pattern recognition and planning ahead. Your thermometer for the final call on planting day.
Different planting operations happen at different depths, and soil temperature varies significantly from the surface down:
The most volatile layer. Swings dramatically with sun, shade, rain, and wind. This is what determines whether a tiny seed can sprout — but it's also the first to warm up in spring and the first to cool down after a rain event.
Where most direct-sown small seeds live: carrots, beets, lettuce, radishes. More stable than the surface but still responds meaningfully to weather. The standard measurement depth for seed germination tables.
The agronomic standard. This is the depth most soil thermometers measure, and what most planting guides (and university extension recommendations) refer to when they say "soil temperature." Tomatoes, peppers, warm-season transplants — this is what matters.
Barely changes day to day. This is a slow seasonal signal — useful for understanding your soil's thermal inertia and for deep-rooted perennials. It's also the depth least affected by surface weather events.
Yes — and SoilIQ models it. A significant rainfall event cools the soil surface more than a model would predict on its own, because rainwater is usually cooler than summer soil and because wet soil evaporates faster. SoilIQ applies a precipitation cooling adjustment to each depth layer after rain events, scaled by the amount of rain and how wet the soil already was.
The practical effect: after a heavy rain, the app will show a more meaningful temperature drop — particularly at the surface — than you'd see from a weather model that hasn't been adjusted for that event.
The 0–100 score on the Today tab is a composite that blends five factors: how close current soil temperature is to your primary crop's ideal range, whether temperatures are trending in a favorable direction, how current conditions compare to historical averages for this time of year, soil moisture adequacy, and recent precipitation stress. It's designed to give a single at-a-glance read on whether conditions are working for you or against you — not as a scientific measurement, but as a practical planning signal.
Open the app, let it find your spot, and see what your soil is actually doing right now — at four depths, with a 14-day forecast.