Below I have included the Environmental and Route Condition Assessment that I assembled for a Backpacking Fundamentals course in Yosemite. It is a good template to use in assessing the likely environmental and route conditions for upcoming trips of your own.
Read this post for or an explanation of why and how to assess environmental and route conditions. You will notice that the assessment below does not contain every possible detail, since this was a relatively straightforward trip in familiar terrain during a friendly time of year. If the trip had been longer in duration or distance, had bigger risks or more variability, or presented a new environment or season, I would have done a more exhaustive assessment.
For the month of June, average temperatures in Yosemite Valley are:
- Average high: 73 F
- Average low: 42 F
The weather station in Yosemite Valley is at an elevation of 4,018 feet. Our route is generally between 7,000-8,000 feet, which equates to a 12- to 16-degree temperature difference, assuming 4 degrees of change for every 1,000 vertical feet in Yosemite’s semi-arid climate. (For a more humid climate, I would have assumed 3 degrees; for an arid climate, 5 degrees). Therefore, if we experience average conditions, we should expect:
- Average highs of around 60 degrees
- Average lows around freezing
In the month of June, Yosemite Valley on average sees 1.48 inches of precipitation.
Our route receives more precipitation, since it’s higher and colder. But, even if our route receives twice as much precip, that’s only 3 inches, which makes precip during our trip possible but unlikely. If there is precip, it is probably a nasty late-winter storm with a mix of rain and snow — let’s hope we avoid one.
Note: Since we are only out for three days, we will be able to get a fairly accurate weather forecast immediately before we leave.
We will have ample daylight to complete our daily mileage goals without having to turn on our headlamps. We’ll have more than 15 hours:
- Begin civil twilight: 5:22 a.m.
- Sunrise: 5:52 a.m.
- Sun transit: 1:01 p.m.
- Sunset: 8:11 p.m.
- End civil twilight: 8:41 p.m.
Phase of the Moon on 18 May: waning crescent with 4% of the Moon’s visible disk illuminated.
We will be hiking primarily on trail. The trail is a mix of dirt, loose cobbles, and rock slabs. Later in the season these trails get very dusty, but that should not be an issue for our early-season trip.
When we hike off-trail, the footing will be mostly the same, though probably fewer loose rocks because off-trail areas are not as eroded.
Source: Photos geotagged near our route (viewable in Google Maps)
Our route is mostly in the Upper Montane Forest, which in Yosemite is generally between 6,000 and 8,000 vertical feet.
Red firs and Ponderosa pines will tower above us, while the forest floor will be relatively free of vegetation, save for pockets of scratchy chapparel. There will be many sunny overlooks and gaps in the tree cover, especially when hiking on granite slabs.
When hiking off-trail through chapparel, pants are recommended.
Good campsites (i.e. protected, soft, good drainage, flat, and free of undergrowth) should be easy to find.
Sources: Yosemite National Park website, topographical maps, and photos geotagged near our route (viewable in Google Maps)
When hiking through forest, visibility will be limited. It will be better when the trail crosses granite slabs, though our route generally lacks high points with sweeping vistas.
Since we will be in a National Park, trail quality and signage should be good. Beware when approaching high-use areas (such as Yosemite Point) due to use/social trails.
Source: topographical maps, past personal experience in National Parks
Sun exposure will be moderate. While our route is fairly high (maximum elevation of 7,000 feet) and the sun is high in the sky (it’s mid-May), there will be ample shade available.
Source: Topographical maps, plus photos geotagged near our route, viewable on Google Maps
There should be plenty of water, as the route follows and crosses many streams and side-streams. Some of these sources are seasonal, but since the winter snow just recently melted off they should be full.
Source: topographical maps, National Snow Analyses
Black bears are a chronic problem in Yosemite, especially at popular backcountry campsites. In fact, the Park Service requires that all backcountry users store their food in bear-resistant containers.
In addition to the bears, there are also problems of “mini bears” at popular campsites. Raccoons, squirrels, rabbits, etc. are almost as good as bears in stealing food and chewing apart salty gear (e.g. shoulder straps, trekking pole grips, etc.)
Source: Yosemite National Park website
Mosquitoes in Yosemite can be pretty bad. Not Alaska bad, but bad, definitely enough to warrant full-coverage clothing and a headnet during peak season.
Usually the bugs are worst shortly after the snow melts off, when there are ample puddles of snowmelt for them to breed and once temperatures are warm enough. Once the puddles evaporate or drain off, the bugs subside, though they continue to be a nuisance near perennial water sources.
The snow melted off our route just recently; we may still encounter a few lingering patches on north-facing and leeward slopes. So, it is possible that we will be there for the first hatch, but we’re likely ahead of it — temperatures are not quite warm enough yet.
Source: Brian Robinson, Yosemite backcountry ranger, and National Snow Analyses
There are overlooks of Yosemite Valley along the route that are surrounded by vertical cliffs. Beware here!
We will be crossing Yosemite Creek, which at this time of year is swollen with snowmelt. However, this past winter was a low snow year and its flow should be less than average. Plus, there’s a bridge over the creek just upstream of Yosemite Falls.
We will not be in any avalanche terrain.
Source: topo maps, Brian Robinson, SNOTEL data
We are starting from a popular trailhead and using popular trails. However, do not expect cell reception, even along the rim of Yosemite Valley (where there is a cell tower).
And, remember, there is no such thing as a fast search and rescue.