WateringHold
Skip watering this week
Expected rain meets the 1.5-inch weekly target, so no irrigation is needed.
View detailsLoading soil temperature data
Conditions, history, and source details
89
Depth: 2" • Last 12 Months
Isabela (Site 2052), PR
USDA NWCC AWDB soil temperature observations.
| Date | 2" °F | Δ 2" | 4" °F | 8" °F | 40" °F |
|---|---|---|---|---|---|
| Aug 17 | — | — | 88.5 | 94.1 | 88.9 |
| Aug 16 | — | — | 86.4 | 92.8 | 88.9 |
| Aug 15 | — | — | 87.4 | 93.7 | 88.7 |
| Aug 14 | — | — | 88.9 | 93.7 | 88.7 |
| Aug 13 | — | — | 87.1 | 92.5 | 88.7 |
| Aug 12 | — | — | 84.4 | 90.3 | 88.7 |
| Aug 11 | — | — | 82.8 | 90.0 | 88.7 |
Soil temperature by depth
Zone 13A
—
390 ft
Warm-season only
This area favors warm-season grasses; cool-season grass struggles through the summer heat here. As of August 20, the 2-inch soil temperature is running 5°F above the 10-year normal for this date. Data comes from the USDA station at Isabela, 21 mi away.
For established lawns and gardens, the 4 inch soil temperature is a more useful reading than the surface. This 4-inch root-zone depth changes more slowly than the 2-inch surface layer, so it is a steadier signal for timing fertilizer, aeration, and weed control. The depths your nearest station reports are shown above; stations in the federal network typically report 2, 4, 8, 20, and 40 inches, while modeled estimates for areas far from a station cover fewer depths.
This week’s watering for Arecibo, PR
Skip watering this week — rain covers it
| Weekly target | 1.5 in | at 89°F soil, for warm-season grass |
|---|---|---|
| Expected rain | 1.65 in | over the next 7 days |
| You supply | 0 in | no irrigation needed this week |
The weekly target includes rainfall, so irrigation only covers the deficit. Water deeply and infrequently rather than a little every day: shallow daily watering builds shallow roots and invites disease. Rainfall is a modeled forecast estimate for this location.
How to water by soil temperature, and audit your sprinklers →
Lawn disease risk
The 7-day forecast near Arecibo, PR favors active disease pressure. These diseases are the ones to watch now. Based on a modeled weather estimate for this location.
| Disease | Risk | Why now |
|---|---|---|
| Pythium blight (Pythium spp.) | Favorable | 7 of the next 7 nights stay above 65°F with hot days; worse with excess nitrogen. Water early morning to limit leaf wetness, hold nitrogen to 0.25 lb/1,000 sq ft, and fix drainage in low spots. The fastest killer, 2-3 days. |
How temperature drives lawn disease, and the cultural fixes →
Soil temperature readings on this page cover 3 ZIP codes in Arecibo, PR:
00612, 00613, 00614
Know when to seed, fertilize, and stop crabgrass at your address. The timing here comes from live in-ground readings at your nearest USDA or NOAA monitoring station, not from the calendar.
Check the current soil temp at your location, or open the live US soil temperature mapto see today’s ground readings from 380+ USDA and NOAA stations across the country. Enter your city or ZIP code for live soil temperatures near you, plus planting windows, pre-emergent timing, fertilizer guidance, and disease watch alerts based on your nearest USDA monitoring station.
Readings refresh nightly from the USDA-NRCS Soil Climate Analysis Network and the NOAA US Climate Reference Network (USCRN). Readings are measured by in-ground sensors at federal monitoring stations, not estimated from weather models; see how we measure. Planting windows are derived from multi-year climatology, overlaid with NOAA 1991–2020 frost normals where a station is close enough to support a local frost date. Recommendation cards evaluate current soil conditions against research-backed thresholds from university extension sources. Check back regularly as conditions change. The guidance updates with every new reading.
Data sources: USDA-NRCS SCAN network, NOAA USCRN, NOAA 1991–2020 climate normals, and localized frost climatology via Soil Temps analytics.
Browse soil temperature data by state, over 2,000 cities with current readings, hardiness zones, and planting windows.
Explore the US Soil Temperature Map for a live station view of readings across the country.
Current soil temperature: 89°F at the 4-inch depth, 4.8°F above the historical average for this date. Measured August 17, 2026 at the Isabela USDA station, 21 miles away.
Current conditions in Arecibo, PR
89°F
4-inch depth
Expected rain meets the 1.5-inch weekly target, so no irrigation is needed.
View details7 of the next 7 nights stay above 65°F with hot days. This is a conditions indicator, not a diagnosis or prediction.
View detailsThe 4-inch reading is 89°F. Check the species table before deciding whether to seed.
View detailsAir and rain
Weather context
Check the current 2-inch reading at the top of this page against the germination bands: cool-season grasses need 50–65°F and warm-season grasses need 65°F or higher, held for several consecutive days.
Soil temperature outside the germination band is the most common cause. Cool-season seed germinates at 50–65°F and warm-season seed at 65°F or higher; outside those bands seed sits dormant rather than sprouting. If the temperature is right, the usual culprits are seed buried too deep, topsoil that dried out during the sprout window, or a pre-emergent herbicide applied the same season, which blocks grass seed the same way it blocks weeds.
Cool-season grasses like fescue and bluegrass germinate best when soil at 2 inches stays between 50–65°F for several consecutive days. Warm-season grasses like Bermuda and Zoysia need soil temperatures of 65°F or higher before seeding. If you are seeding, a high-phosphorus starter fertilizer goes down in the same window; regular established-lawn fertilizer follows different timing.
Apply pre-emergent herbicide, the product sold at retail as crabgrass preventer, when soil at 2 inches reaches 55°F for several consecutive days. This is the threshold where crabgrass and other summer annual weeds begin germinating, and applying after that point reduces effectiveness significantly. Weed-and-feed products that include a pre-emergent follow the same window. The pre-emergent timing page for Arecibo tracks this threshold against the current reading.
Arecibo, PR is in USDA hardiness zone 13a, mild enough that warm-season grasses like Bermuda, zoysia, and St. Augustine come through winter reliably; they go tan and dormant rather than dying. Cool-season grasses survive winter here easily but struggle through the hot summer instead.
Use 2 inches for germination decisions, since that is where seeds sit. Use the 4 inch soil temperature for established lawn and garden timing: it reads the root zone, changes more slowly than the surface, and is the depth most fertilizer, aeration, and disease guidance references. The 8 inch reading shows deeper root-zone trend. The 20 and 40 inch readings track deep soil and frost depth where federal stations report them.
Soil changes temperature much more slowly than air due to thermal mass. A warm afternoon does not mean the ground is warm. Soil temperature lags air temperature by days or weeks, making it a more reliable indicator of when biological processes like germination actually begin.
It is a direct ground measurement. Soil Temps reads from 337 active USDA and NOAA in-ground monitoring stations, which report daily at depths from 2 to 40 inches.
Grass seed germination
Your soil near Arecibo, PR: 89°F at 4-inch (2-inch unavailable), as of August 17, 2026.
| Grass species | Seeding soil temp (2 in) | Days | Right now |
|---|---|---|---|
| Bermudagrass | 75–90°F | 10-30 | Germinates well |
| Zoysia | 75–90°F | varies | Germinates well |
| Buffalograss | 75–90°F | 14-30 | Germinates well |
| Centipede | 75–90°F | varies | Germinates well |
| Kentucky bluegrass | 60–70°F | 14-30 | Too warm to establish |