Turf light (DLI) checker
See how much light your green gets over its growing season, compared with published research for your grass.
Free to use. No sign-up, no email.
Or enter coordinates — any map app shows them.
Season light on the green (May–Oct)
Loading the solar data…
Method: real-weather light for open ground from NASA POWER (2001–2025 average), multiplied by the green's share of the day in direct sun (the hours-of-sun method our shade and light reports use), averaged over the grass's research season and set against the published threshold. Modeled, not a meter reading. Solar data: NASA POWER (power.larc.nasa.gov). ZIP codes are placed at the centre of their 3-digit ZIP area, from US Census ZIP Code Tabulation Areas.
How the turf light checker works
Light at the course in full sun, each month
Open-site DLI (mol/m²/day) = NASA POWER all-sky sunlight (MJ/m²/day) × 2.0184
All-sky means real weather, clouds included. The value comes from NASA's 1° grid cell around your location; 2.0184 turns sunlight into plant light (Faust & Logan 2018).
Light on the green, on the 21st of each month
Green DLI = open-site DLI × (hours of direct sun ÷ daylight hours)
Daylight hours count 30-minute steps with the sun at least 5° above the horizon. Hours of sun above daylight count as full sun.
Season light and rating
Season light = average of the monthly green DLI over the research season (bentgrass May–Oct, ultradwarf bermudagrass Jun–Aug)
Adequate: at least 1.1 × the threshold. Adequate (borderline): adequate but within 10% of the threshold. Marginal: at least 22 (bentgrass) or 24.6 (ultradwarf). Critical: below that. The Marginal and Critical bands are the planning bands our shade and light reports use, not research values.
Fall light
Fall light = average of the monthly green DLI, Sep–Nov, shown against 19–25 mol/m²/day
The published bermudagrass fall range, shown as a reference, not a grade.
Where the numbers come from
- Real-weather sunlight at the course: NASA POWER all-sky surface shortwave (ALLSKY_SFC_SW_DWN), monthly climatology 2001–2025 from CERES SYN1deg, Climatology API v2.10.1, accessed November 1, 2026. NASA POWER (power.larc.nasa.gov), Referencing Guide
- Sunlight to plant light (PAR): 0.0072664 mol of photons per Wh of solar radiation, which is 2.0184 mol per MJ. Faust & Logan (2018), “Daily Light Integral: A Research Review and High-resolution Maps of the United States”, HortScience 53(9):1250–1257
- Creeping bentgrass putting green: 30 mol/m²/day, season average May–October ('Tyee', University of Arkansas). Russell, Karcher & Richardson (2019), Crop Science 59(4):1768–1778
- Ultradwarf bermudagrass putting green: 32.6 mol/m²/day, season average June–August ('TifEagle', Clemson). Bunnell, McCarty, Faust, Bridges & Rajapakse (2005), Crop Science 45(2):569–574
- Fall light reference: 19–25 mol/m²/day for bermudagrass in fall (Sep–Nov), the range our shade and light reports use — a reference, not a grade. Chen, Wherley, Reynolds, Hejl & Chang (2021), Crop Science 61(4):2837–2847
Worked example (the checker opens with these numbers)
- A creeping bentgrass green at latitude 36.6°N, longitude 93.8°W, with 10 hours of direct sun on a clear day.
- NASA POWER, July: 22.94 MJ/m²/day × 2.0184 = 46.30 mol/m²/day in full sun.
- July 21 has 13 daylight hours, so the green gets 46.30 × 10 ÷ 13 = 35.62 mol/m²/day.
- May through October on the 21st: 32.23, 35.63, 35.62, 34.73, 32.55 and 25.57 — an average of 32.7 mol/m²/day.
- 32.7 is at or above the 30 mol/m²/day research threshold but within 10% of it: Adequate (borderline). In full sun the same season averages 40.1.
- Fall (Sep–Nov): 32.55, 25.57 and 19.58 (November 21 has 9 daylight hours, so the green is in sun all day) — an average of 25.9, above the 19–25 range.
Check: for the 18 greens of a course in our shade and light reports, this math gives the same season light as the report within 0.1 mol/m²/day, and the same rating on every green, when it gets each green's hours of sun month by month.
Questions about the turf light checker
What is the daily light integral (DLI)?
The daily light integral is the total light useful to plants that reaches a surface in one day, counted in moles of photons per square metre.
Is the turf light checker a measurement?
No. The turf light checker models light from NASA's real-weather sunlight record for your area and the hours of direct sun you enter. It is not a meter reading.
Why a season average and not a single day?
The research thresholds were set over a season: May to October for creeping bentgrass and June to August for ultradwarf bermudagrass. The turf light checker averages the same months.
How do I find the hours of direct sun on my green?
Count the hours the putting surface is out of shade on a clear day, or enter them month by month if you know them. Our shade and light analysis models them for every green from a drone survey.
Does the turf light checker send my location anywhere?
No. The solar data and the ZIP code table are files served from this site, and the math runs on your device. Nothing you type is sent or stored.
Want this for every green on your course?
Our shade and light analysis models the hours of sun on every green from a drone survey, month by month, and shows which trees shade each one.
Questions? info@aetherisintel.com