Wisconsin Elevation ToolsOpen Sunlight on the map →

Terrain · Select a property, draw a box or polygon, or upload a boundary

Winter sun hours on any Wisconsin lot

See the winter sun hours on a lot in Wisconsin before you buy or build. The tool traces the sun across any day of the year in 15-minute steps and checks whether terrain up to 1.86 mi away, and optionally the trees and buildings in Brown County’s regional surface model, block it.

December 21, the shortest day, is the test that matters for a house site: a lot can look sunny at a July showing and lose the sun behind a ridge or a stand of firs by early afternoon in winter. South-facing ground gets the most.

Free to run · pay to download

See the full result on the map free, with no account. Download the sun-hours grid as a GeoTIFF with a pass: US$29 for 24 hours, US$99 for 30 days or US$399 for 12 months, a one-off payment in US dollars that never renews. Every download on the site is included while the pass lasts.

Open Sunlight on the map →Pass prices and what’s included

Who uses this

  • Buyers. Check winter sun on a lot before a summer showing fools them.
  • Architects. Place living areas, decks and windows where the winter sun actually reaches.
  • Growers and solar installers. Find frost pockets and the ground that stays lit in December.

When to use it

  • Checking winter sun on a house site, a deck or a garden before you buy or build.
  • Comparing sunny and shaded parts of a property for planting or livestock.
  • Seeing when the sun first reaches a valley floor and when it leaves.

Tools for your job

Sunlight is one step in a bigger question. These are the jobs it helps with, and the tools that go with it.

For the job: Solar panels and sun

Where will panels, a greenhouse or a deck get the most sun?

  1. 1.Sunlight (this tool) — Hours of direct sun on any date, with terrain shadows from up to 1.86 mi away. Start with December 21.
  2. 2.Slope & Aspect — The aspect view shows which faces point south, and the slope view how steep the mounting ground is.
  3. 3.Find Matching Areas — Highlights the ground that is flat enough, faces the right way and gets a minimum of winter sun, all at once.
  4. 4.Object Heights — Tree and building height estimates where Brown County surface data is usable; inspect shading on site elsewhere.

For the job: Choosing a house site

Where on this property should the house go?

  1. 1.Find Matching Areas — Narrows the property to the patches that are flat, sunny and facing the right way.
  2. 2.Slope & Aspect — Shows gentler and steeper ground for a designer to assess.
  3. 3.Sunlight (this tool) — Checks winter sun on the candidate pad, hour by hour.
  4. 4.Cut & Fill — Estimates the excavation to level the pad before you ask for bids.
  5. 5.Viewshed — Models terrain visibility from a chosen eye height; surface blocking is regional.

For the job: Farms, ranches, orchards and timber

Which ground suits which use?

  1. 1.Slope & Aspect — Equipment limits and erosion-prone slopes.
  2. 2.Sunlight (this tool) — Frost pockets and shaded slopes in winter.
  3. 3.Wetness Map — Wet-tolerant planting in the blue, drought-tolerant on the tan.
  4. 4.Landforms — Exposed ridges, sheltered hollows and well-drained spurs.

How to use it

  1. Select a property, draw an area or upload a boundary.
  2. Pick a date: December 21 (the shortest day), an equinox, June 21 (the longest day), or any date you type.
  3. Choose bare ground, or the surface model so trees and buildings cast shadows too.
  4. Run. Read total hours and first and last sun, then step through the day at half-hour marks to watch the shadows move.
  5. Download the sun-hours grid as a GeoTIFF for GIS. Downloading needs a pass.

Step by step: Devils Lake

We model December 21, the shortest day, across Devils Lake and its bluffs.

1.Zoom to the area or select a property. December 21 is the default, because winter sun is the test that matters for a house.

2.Preview on map. The panel shows the hours of daylight that day, the mean hours of direct sun and the share that gets at least three hours. The dark areas sit in terrain shadow.

3.Choose Step through the day and move the slider to see each half hour. The panel also shows when the sun first reaches the area and when it leaves, in Central time.

What it showed

  • South-facing slopes with an open southern horizon get the most winter sun; ground at the foot of a bluff to its south stays in shadow for much of the day when the sun is this low.
  • In Brown County, turn on trees and buildings to include shade from forest and neighbors from the county’s surface model. Elsewhere the tool uses bare ground only.
Try it yourself on Devils Lake →

How it works

The sun’s position is computed for the chosen date every 15 minutes. For every cell the tool traces a ray toward the sun and checks whether any terrain within 1.86 mi rises above it. If nothing blocks the ray, the cell is lit for that step.

Hours of sun add up the lit 15-minute steps. With the surface option, Brown County’s surface model, which includes tree canopy and roofs, is used as the blocking surface instead of bare ground.

Reading the results

December 21 is the test that matters for a house site. A south-facing slope with an open southern horizon will show the most hours.

First and last sun are the clock times, in Central time, when the sun first clears and finally drops behind the horizon for that cell.

Limits and caveats

  • Direct sun only. Cloud, haze, smoke and diffuse light are not modeled.
  • Shadows from anything further than 1.86 mi away, such as a distant ridge, are ignored. In deep canyons the true horizon may be further out.
  • The optional surface model covers Brown County only. Outside usable Brown County data, Sunlight, Viewshed and Sightline fall back to bare earth, so trees and buildings do not count. Object Heights needs usable surface data. Its source date can differ from the 3DEP ground model.
  • Times are shown in Central time throughout Wisconsin, with daylight saving time applied for the selected date.

Data and attribution

Results come from the USGS 3D Elevation Program (3DEP) bare-earth elevation model: lidar at 3.3 ft per pixel where it has been flown, with older lidar at about 9.8 ft per pixel and coarser sources at about 33 ft per pixel elsewhere, with elevations above NAVD 88. The optional surface model is limited to Brown County. Outside usable regional data, Sunlight, Viewshed and Sightline fall back to bare earth; Object Heights needs usable surface data. Surface and ground source dates can differ.

USGS 3DEP elevation data and USGS maps are U.S. Government works in the public domain: you may use the results, including commercially. A credit to the USGS 3D Elevation Program is appreciated, and every file you download carries it. Wisconsin parcel boundaries are aggregated local-government data, not legal surveys; the parcel disclaimer accompanies the selection. Brown County surface data is credited separately when used. The Esri aerial basemap follows Esri’s terms and is display-only; downloadable aerial photos use USGS NAIP.

Questions

Does it include shade from trees and neighboring houses?

Yes, if you choose the surface option. It uses Brown County’s regional surface model, with trees as they stood when the lidar was flown; outside its usable Brown County coverage the tool falls back to bare ground. The bare-ground option shows terrain shading only.

Does it account for clouds?

No. It models direct sun on a clear day. Cloud, haze, wildfire smoke and diffuse light are not included.

What time zone are the times in?

Central time, on standard or daylight saving time as it applies on the chosen date, everywhere in the state.

Ready to try it?

Open Sunlight on the map →

Free to use, no account. The analysis runs in your browser on public-domain USGS 3DEP data. Downloading the results needs a pass: see pricing.