▶ Dial your 2-stroke to the weather. Save a baseline jetting setup — main jet, pilot, needle clip — with the conditions of that run, and Jetting Weather suggests a corrected jet size when the air changes. ▶ Density altitude is what your engine really feels. The app reads the barometer and pulls temperature and humidity, then works out the air density ratio and turns it into a jet-area correction and a size step. ▶ Built for the paddock routine — motocross, dirt bike and kart 2-strokes need a jet swap for the day's air. Log settings per track and compare runs at a glance. ▶ This is a relative advisor, not a factory table. It moves you from a known-good baseline; it does not claim an exact jet for your specific engine. Always confirm with a plug reading. ▶ Works with the barometer plus online weather. Save baselines, review your history, and share a clean setup card. No account needed. Results are estimates based on your baseline and current air. Real jetting varies with fuel, altitude, engine wear and riding. This app does not replace a tuner's judgment — read your plug and test on track.