Groundwind Notes

Field notes on whitetails and the wind

In the rut, bucks come in downwind.

The rut makes him reckless, not noseblind. A rutting buck covers ground, checks does by nose, and when something sounds like a fight he swings round to smell it before he shows himself. Where your scent goes decides whether you see him. Here's what's been measured, what's hunter experience, and what it means for where you sit.

By Gavan. 26 October 2026, a 7-minute read.

The downwind swing

The best study of it ran four seasons at the Welder Wildlife Refuge in South Texas. A rattler sat on the ground, with an observer up a 10 m (33 ft) tower downwind of him. Of the 111 bucks that came, 67 (60%) were first seen downwind. Bucks spotted before the rattling started usually circled to the downwind side on the way in. Fewer came as the wind picked up (Hellickson 2009).

It isn't only whitetails. Reindeer that see a person usually move round to his downwind side, apparently to smell what he is (Baskin and Skogland 1997). And crossing the wind is the textbook way for a nose to search, because it sweeps the most new air (Togunov 2017). Hunters see rutting bucks cruise that way, crosswind and along the downwind side of cover (Infalt, Realtree). No collar study has measured that for whitetails yet.

Rattling with a partner · seen from above, the wind left to right

Seen from above, with the wind blowing left to right. The rattler sits upwind, the shooter 40 to 50 metres downwind of him. Both scent cones run downwind. The buck leaves cover and circles toward the downwind side of the rattling, crossing in front of the shooter before he reaches the scent. WIND buck, in cover he crosses here rattler shooter 40–50 m scent
He swings to smell the fight
Put the shooter on his way there

At the stand

  • Expect him on the downwind side, not where you're looking. Put your shooting lane between you and where your scent goes, inside your range.
  • If the downwind side is a wall of brush, he circles it unseen. Pick a sit whose downwind side you can see into.
  • Rattling with a partner? Put the rattler upwind and the shooter downwind, the way the Welder study had it. A buck swinging to wind the rattling walks into the shooter's lane first.

Creek bottoms: where every slope's scent ends up

From the time a slope loses the sun until the sun is back on it, the cold air lying on it drains downhill (Whiteman 2000; Mahrt 1982). On a wooded Pennsylvania ridge it started about two hours before sunset and slid down the slope at about 0.5 to 1 m/s (1 to 2 mph). In the bottom it pooled. Once the cold pool formed, the wind there fell under 0.5 m/s and wandered every way, while the upper slope kept draining into it all night (Mahrt 2010).

Southern Kentucky, Sun 18 Oct, 8:15 pm
Forecast east, scent drains down the hollow
  • On the side slopes your scent slides downhill from late afternoon on, into the bottom.
  • In the bottom it hangs and wanders. That's the swirl hunters complain about in bottoms, and a buck anywhere in the pool can get it. Where the creek has room to run, the air also creeps downstream: hunters who work bottoms in the rut find it going downstream almost all day on cool days (Martonik, Bowhunter).
  • The pool lasts into the morning. In small basins it took 2½ to 3 hours after sunrise to break up (Whiteman 2004), so a bottom at first light is still an evening bottom.
  • Leaf-off helps. In full leaf a hardwood gully in Indiana ran the wrong way at night, up the gully. In November, with the leaves down, it drained downhill the usual way (Froelich and Schmid 2006). The rut's air is easier to read than September's.
  • Then the switch. Once the sun reaches the slopes, each one turns from draining to rising at its own time (Farina 2023; Nadeau 2020), and the bottom gets air from several directions at once. More on that in hunting thermals.

Thermal hubs

Hunters call it a thermal hub where three or more draws meet in a bottom, and it's often good rut ground (Martonik, MeatEater). The measurements back the name. At dusk each draw brings its own cold air in. In two English valleys the coldest spot on the floor was where side valleys joined (Sheridan 2014). Where a side valley met a main one in Colorado, the flow pulsed back and forth every 8 to 16 minutes (Porch 1989). A hub at dusk is a pool of every slope's air, yours included, and it sloshes.

The hub rule

  • While the air drains, stay off the slopes above a hub. Your scent slides down into the one place every deer passes through.
  • Don't sit in it at dusk or first light, either. Your scent hangs in the pool and goes every way.
  • Hunt it on a breeze. Studies of valley cold pools find they break up once the wind above reaches about 5 to 8 m/s (11 to 18 mph) (Jemmett-Smith 2019). Then the hub follows the wind, and you can sit it like anywhere else.
  • Once the sun is on the slopes, the air climbs out of the hub up every draw. Then sit high, on a point between two draws.

Windy days

Penn State asked more than 1,600 Pennsylvania hunters about wind, and about 90% expected deer to move less when it blows. Their GPS-collared deer said otherwise. In October, bucks moved more on windy days and less on windy nights (Giralico 2015). In a second run of the data, a strong wind of 16 to 27 mph raised buck activity whether it was raining or not (Hepner 2018).

Elsewhere wind hardly mattered at all. In Oklahoma, deer located every 15 minutes showed no general pattern with wind (Webb 2010). In South Carolina, buck activity in the breeding season barely changed with wind speed (Goethlich 2019). You'll read that deer movement drops at 15 to 19 mph. That comes from a 1980s South Texas study known through hunting magazines, and we couldn't find its data.

What wind does measurably cut is a buck's answer to rattling (Hellickson 2009), and noses work worse in it: scavengers took longer to find food as the wind rose (Ruzicka and Conover 2012). Under the trees the wind at your head is still a fraction of the forecast's, even with the leaves down: in a Tennessee oak–hickory forest the wind at 2 m ran at about 15% of the wind above the trees, only a little more in winter than in summer (Wilson 2000). A steady breeze sends your scent one way you can plan around, where a still evening pools and swirls it. Go hunting.

When the rut peaks where you hunt

In the North the breeding peak is mid-November and tight. Going south it gets later and more spread out, and in Georgia and Alabama it changes county by county (Stickles 2015; Turner 2019). Chasing peaks about two weeks before the mean breeding date (MDWFP). The moon has nothing to do with it: Pennsylvania's road-killed does put the median conception date for adult does at 13 November year after year (Diefenbach 2014).

Peak breeding and the 2026 firearms opener by state and province
State or provincePeak breeding2026 gun opener
WisconsinMost fawns conceived 23 Oct – 12 Nov (WDNR)Sat 21 Nov
IllinoisMean 8 Nov, adult does (Green)Fri 20 Nov (IDNR)
OntarioAbout 9 days earlier in the southwest than the northeast (Newton)Mon 2 Nov (central, eastern and southern WMUs) (Ontario MNR)
OhioMost adult does bred 3–23 Nov (Tonkovich)Mon 30 Nov (ODNR)
PennsylvaniaMedian 13 Nov, adult does (Diefenbach)Sat 28 Nov
KentuckyAbout 14 Nov (KDFWR)Sat 14 Nov
MichiganJust before the firearm opener (MDNR)Sun 15 Nov
New YorkMid-November (DEC)Opened Sat 24 Oct (Northern Zone), Sat 21 Nov (Southern)
KansasMid-November (KDWP)Wed 2 Dec
MissouriMean 16 Nov, adult does (Hansen)Sat 14 Nov (MDC)
IowaAbout 22 Nov, 2½-year-old does (Haugen)Sat 5 Dec (Iowa DNR)
MinnesotaNovember to early December (MN DNR)Sat 7 Nov
TennesseeNovember (TWRA)Sat 21 Nov
QuébecNovember and December (MELCCFP)Opened Sat 17 Oct (shotgun, most southern zones), Sat 7 Nov (rifle)
GeorgiaBy county, mid-October to late December (WRD rut map)Opened Sat 17 Oct
AlabamaBy area, 10 Nov to 8 Feb (ADCNR rut map)Sat 7 Nov (zones D, E), Sat 21 Nov (A, B, C)
TexasBy region, 30 Sep on the coast to 24 Dec in South Texas (TPWD)Sat 7 Nov

Season dates as each state or province published them for 2026; check your own unit's before you go.

Check it from the stand

Every rule here is a guess until you check it where you sit. Puff your powder when you get in, again when the light changes, and again when the sun reaches the slopes around you. Let a milkweed seed go to see where the air takes your scent past the powder.

"Prepare as much as you can, bring the best tools you can to the hunt, and adjust it while you're out there. The best plans don't survive contact with the real world."

See the rut's wind on your own ground.

Groundwind is a hunting app that works out the wind at head height for your spot, over the LiDAR ground and every stand of trees: cold air draining down each draw, the sun coming onto each slope, the lee of a ridge. Your scent cone follows it, from the ground or a stand, and a puff of powder corrects it. It works with no service.

Get your spot built Try it on our spots

Want to read more? Here's the research.

Every figure on this page comes from one of these, and each title links to the source. Hunter experience is marked as such. For the downwind swing, start with Hellickson's rattling study: it's free and four pages long.