Loam
Start with the closure, then check the dirt
A land manager's closure notice settles the question. State parks, county parks, and DNR-managed forest each post their own, and they take priority over anything else on this page. If the network is open, use Loam's condition estimate as a second check. Weather in this region can shift over a few miles of elevation, so pay attention to what you find at the trailhead too.
The short version
Check the official closure first. Read the network condition next. Turn around if the tread is soft enough to hold a rut.
A fixed rule like "give it two days" misses too much here. Some networks sit low and open near the water, where wind and sun get at the tread quickly. Others climb into dense conifer forest where the ground barely sees direct sun in winter. The storm was shared. The drying time was not.
What changes the drying time
Recent rain
Amount matters, but timing does too. A morning shower can matter more than a bigger storm several dry days back, and Puget Sound weather runs light and frequent from October through May rather than arriving in a few big events.
Soil and rock
Much of this region sits on glacial till and clay left behind by the ice sheets. Fine material like that holds water near the surface longer than looser or rockier ground.
Sun and canopy
Canopy across the region's networks runs from 37% up to 84% cover. Open ground dries with help from sun and wind. Under a dense conifer canopy, the tread gets less of either, especially on short winter days.
Slope and drainage
Water moves off steeper ground faster. This region ranges from trails with almost no pitch to grades above 17°, and elevation spans from just above sea level to nearly 1,000 meters. Flat lowland corridors and low spots can stay soft well after a steep section looks ready.
A regional pattern, not a ranking
Seattle-area networks share the same maritime climate, but their ground is not interchangeable. Low corridors near the Sound, forested foothills east of the city, and higher terrain toward Snoqualmie Pass all respond differently to the same system moving through.
That does not make one network a reliable wet-weather fallback. The safe choice still depends on its current closure status and condition. Loam scores each network from its own canopy, slope, elevation, and recent weather instead of applying one regional timer.
How to check after a storm
Open the network page
Look at the current verdict, recent rain, and the ground traits behind the estimate.
Confirm the land manager's notice
Closures and posted restrictions from the state park, county, or DNR take priority over a modeled condition.
Check again before leaving
A passing shower can change the surface after an earlier reading, and this region gets a lot of passing showers.
Read the tread at the trailhead
If tires sink, leave a rut, or pick up wet soil, give the network more time.
Seattle & Snoqualmie network conditions
These Loam pages show the latest modeled condition and any closure data available for the network.
Canopy near 75% on nearly flat ground (1.3° slope) at a low 104m, so drainage does more of the work here than shade or grade.
Heavy conifer cover (81% canopy) over flat, low-elevation ground (132m, 1.5° slope), a shaded lowland network with little grade to help water move off.
Similar profile to the region's other Sound-side parks: canopy near 66%, flat grade (1.8° slope), low elevation (141m).
Canopy near 75% on a gentle 2.1° grade at 191m elevation, closer to the region's shaded, low-grade norm than its name suggests.
The most heavily shaded network in the region (84% canopy) and one of the steepest (13.6° slope), at a higher elevation (471m) than the Sound-side parks.
Sits among the lowest elevations in the region (71m), with canopy near 79% and gentle grade, typical of the parks closest to the water.
The flattest network in the region (0.2° slope), so its dense canopy (79%) has far more say over drying than grade does.
The lowest elevation in the region (64m), with moderate canopy (71%) and almost no grade to move water off flat ground.
Heavily shaded (82% canopy) and the second steepest network in the region (14.7° slope) after Rattlesnake Mountain, at 238m, a combination that keeps the tread slow to dry.
High canopy (83%) partway up in elevation (714m), with enough slope (6.8°) to help move water off the shaded tread.
The steepest network in the region (17.1° slope) and among the most forested (82% canopy), at 737m, a combination where grade and shade pull in opposite directions.
The highest network in the region by a large margin (980m), with steep grade (14.2°) and heavy canopy (77%) up near Snoqualmie Pass.
Canopy near 73%, below the region's median but far from open, at a low-lying 133m elevation.
Dense conifer cover (82% canopy) over a moderate 7.8° grade at 727m, a foothill network that drains at a decent clip but stays shaded and slow to dry underneath.
High canopy (78%) with real grade (8.4° slope) at a modest 168m, between the region's steep shaded foothills and its flatter lowland networks.
The most open network in the region by a wide margin (37% canopy), on low, gently sloped ground (68m, 1.7° slope) where sun and wind reach the tread directly.
The science behind the estimate
Loam starts with a simple physical fact: a trail does not dry just because the rain stops. Water has to enter the ground, move through or across the soil, and leave the trail environment. How quickly that happens depends on the soil, terrain, vegetation, recent weather, and how wet the ground already was.
Soil controls infiltration
Soils do not accept water at the same rate. USDA hydrologic soil groups range from high-infiltration soils such as deep sands and gravels to very slow-infiltration soils associated with clay, high water tables, or restrictive layers. Typical infiltration-rate ranges used in the hydrologic-group framework run from more than 0.30 in/hr for Group A to less than 0.05 in/hr for Group D when thoroughly wet.
Previous rain still matters
A storm does not start with an empty soil profile. USGS notes that soil already saturated from previous rainfall cannot absorb much more, so a larger share of the next storm becomes runoff. Recent weather therefore matters even when the latest storm was not especially large.
Terrain changes the water path
Slope changes how quickly water can move away from a surface. Low spots, drainage features, and trail geometry can change where water collects or leaves the tread. Soil classification and slope are separate pieces of the landscape, which is why both matter to a trail-condition model.
Drying is a water budget
After rainfall, water can remain in the soil, move downward or sideways, run off, or return to the atmosphere through evaporation and plant transpiration. Soil-water-balance models use these processes to estimate changing soil moisture and net infiltration over time.
Why Loam is not a rain timer
There is no useful rule that says every trail becomes rideable after the same number of dry hours. Starting moisture, infiltration behavior, terrain, canopy, and weather after the storm all change the answer.
That is the problem Loam is designed to estimate. The model combines public soil and terrain information with recent weather and network characteristics to estimate how conditions are changing. It is a model of likely trail conditions, not a sensor embedded in the dirt, and it never overrides an official closure.
What the research says
USDA and USGS hydrology work treats infiltration, soil moisture, runoff, canopy, land cover, slope, and evapotranspiration as interacting parts of the water cycle. Recent trail research adds an important piece: rainfall intensity and accumulated rainfall can strongly affect runoff and sediment generation on recreational trails, while wet conditions make trail surfaces more vulnerable to degradation.
USDA NRCS: Hydrologic Soil Groups
Soils are classified by infiltration and runoff behavior when thoroughly wet. The framework distinguishes four main groups and dual drained/undrained classes.
NRCS National Engineering Handbook →USGS: Infiltration and the Water Cycle
Explains how soil characteristics, saturation, land cover, slope, and evapotranspiration affect where precipitation goes.
USGS Water Science School →USGS: Soil-Water-Balance
A published water-budget model that estimates soil moisture, net infiltration, evapotranspiration, and canopy interception from gridded environmental data.
USGS SWB Version 2.0 →NRCS: RUSLE2
A USDA model for estimating soil loss caused by rainfall and associated overland flow, connecting rainfall and runoff to erosion risk.
USDA NRCS RUSLE2 →Fang & Ng, Journal of Environmental Management, 2026
A year-long field study found cumulative rainfall and maximum daily rainfall predicted runoff and sediment yield on recreational trails, with maximum daily rainfall the stronger predictor in that study.
Read the research →These sources describe the physical processes and research Loam draws from. They do not describe Loam's proprietary model or disclose its weights and thresholds.