Weather apps have a tendency to alienate their user bases, perhaps because people’s physical experiences—their plans, their dress, their commutes—so directly depend on an accurate report. As Jonas Downey, the co-founder of an app called Hello Weather, told me, “It doesn’t take much for the app to lose trust with someone.” One unforeseen storm might send users looking for an alternative. Ever since Dark Sky shut down, Downey added, “There’s been this absence in the market.” Acme (which has a subscription-based model, at twenty-five dollars a year) is less cluttered than Dark Sky by design. When you open the app, you are presented with the weather “Right Now,” the forecast for the “Next 24 Hours,” and the forecast for the “Next 10 Days”; each is listed under a bold text banner that resembles a print newspaper headline. The twenty-four-hour temperature forecast is shown as a fluctuating black line tagged with icons denoting the weather every three hours. Crucially, though, there are alternate forecasts that appear in the form of paler gray lines; sometimes the gray lines hew closely to the main black one; other times they stray considerably, indicating that the predictions are less reliable during that window. As Grossman put it to me, “Climate change is causing an increase in uncertainty. It sucks that we can’t predict the weather perfectly, but knowing that uncertainty is very useful.” He cited, as an example, one recent day in his home state of Connecticut, when the forecast predicted snow in the morning and rain in the evening; in between, the conditions were harder to pinpoint. Acme dealt with this by displaying alternate forecast lines for both rain and snow, coded in different colors—a visualization that doubled as an admission that the forecast that day was a bit of a mess.