“Planning” hikes and treks with smartphone apps is quite easy. The FarOut app and the PDF file of the AT Guide also apply to planning hikes on the AT, both for thru hikers and section hikers. While I use a Gaia GPS subscription for navigating and recording my day hikes, I prefer the free version of AllTrails for researching potential day hikes. AllTrails search function, maps, reviews, photos, and ability to save favorite hikes all give a comprehensive overview of hiking trails. AllTrails is nationwide; but many local trail organizations have their own similar app. We are planning a trip to the Pacific Northwest in September; so, right now, I have the trails app from the Washington Trails Association on my phone. I also rely on the National Park Service app for planning hikes and trail alerts in national parks. Many national parks now require day-use or backcountry permits for hiking and backpacking; therefore, Recreation.gov app is helpful for making those reservations. Weather is a particularly important planning factor, both before the trailhead and while on the trail. I use the Weather.com app for my weather forecasts; I find this app to be the most consistent and accurate available. I also use RadarX weather app. I use this app a lot on my boat for tracking storms and found that it also is useful over land. The radar tracks of storms are extremely accurate to within less than a mile. Unfortunately, both these apps require either WIFI or mobile data.