Sources
Sources and methods
Every number on Soil Temperature Map comes from the public datasets below. Each page names the ones it uses at the bottom.
- NOAA National Centers for Environmental Prediction (NCEP). Analyses at 00/06/12/18 UTC since 1 January 2026 and the newest 7-day run (Nov 11, 12:00 UTC (7 am Eastern)), read from the NOAA GFS bucket of the NOAA Open Data Dissemination program (same files as NOMADS). Only the 0–10 cm soil temperature record is used, at each city's nearest land grid cell.Licence: NOAA open data (NOAA Open Data Dissemination): open to the public and may be used as desired; NWS information is public domain. Attribution requested; no NOAA endorsement implied. · cited on 34,605 pages
- NOAA National Centers for Environmental Information (NCEI). Hourly files for 108 stations, 2025 and 2026. Used for the measured 2 in / 4 in readings and to measure the model's error.Licence: U.S. Government work, not subject to copyright; public domain. · cited on 656 pages
- NOAA National Centers for Environmental Information (NCEI). Daily highs and lows from 1 October 2024, via the NCEI Access Data Service (daily-summaries). Used for growing degree days and chill hours.Licence: U.S. Government work, not subject to copyright; free to use with citation (Menne et al. 2012, doi:10.7289/V5D21VHZ). · cited on 1,323 pages
- GeoNames. City names, coordinates, populations and time-zone ids.Licence: CC BY 4.0 · cited on 1,516 pages
- U.S. Census Bureau. ZIP code centre points (ZCTA internal points) and land area; generalised state outlines for the map and for placing each ZIP in its state.Licence: U.S. Government work, public domain. · cited on 33,547 pages
Method
Every soil reading on this site is the 0–10 cm (0–4 inch) soil layer of NOAA's Global Forecast System (GFS), the U.S. National Weather Service's global weather model, on its 0.25° grid (about 25 km between grid points). Each city uses the nearest land grid cell; the page gives the distance. Cities whose nearest land cell is more than 30 km away (small islands, long sandbars) get no page.
- Past days come from the model's analyses at 00, 06, 12 and 18 UTC. The next 7 days come from the newest run (every 6 hours of it). A day is the average of the four values at 06, 12 and 18 UTC and 00 UTC the next day (about 1 am to 7 pm Eastern); the low and high are the lowest and highest of those four.
- Thresholds and dates use the 5-day running mean of those daily averages, so one warm afternoon does not open a window. "Held 55°F from 3 April" means: the first day of the spring when the 5-day mean stayed at or above 55°F for at least 10 days running, after being below it.
- Measured 2 in and 4 in readings come from NOAA's U.S. Climate Reference Network (USCRN): buried probes at 5 cm and 10 cm, reported every hour. They are shown only for the nearest station within 150 km and are never mixed into the model numbers.
- Growing degree days (base 50°F, simple average method: (high + low) / 2 − 50, never below zero) and chill hours come from NOAA NCEI GHCN-Daily highs and lows at the city's nearest station that reports at least 96% of days. Gaps of up to 5 days are filled by straight-line interpolation. Chill hours are hours at or below 45°F from 1 November, estimated hour by hour from each day's high and low (a cosine curve from the low at 6 am to the high at 3 pm and back); the hours between 32 and 45°F are shown as well.
A model is not your lawn. Sun, shade, slope, mulch, irrigation and soil type move a real lawn's temperature by several degrees. The measured error against the reference stations is on this page; for a single yard, a $15 soil thermometer pushed in 2 to 4 inches is the best check.
The garden thresholds (50 to 55°F for crabgrass pre-emergent, 50 to 65°F for cool-season grass seed, 65°F for warm-season grass, 60°F for tomatoes, 40°F for peas and lettuce) are common rules of thumb from lawn and garden guidance, not product instructions. Follow the label of any product you apply. This site is not affiliated with or endorsed by NOAA or the National Weather Service.