Picking what to wear for a run in the fall is often a game-time decision—you just never know what the weather will be until you’re ready to walk out the door. But no matter how last minute, sometimes those apparel choices come back to haunt you during your workout—an extra hoodie can be annoying if the sun pops out, and unforeseen wind gusts can leave shorts-clad legs chillier than you’d like. That’s why planning a race outfit can be daunting. If you’re not sure what to wear, consider this your head-to-toe guide!

The first rule for race wear: don’t put on anything that you haven’t run in before. That goes for your socks, too. It’s just too hard to tell if a brand new pair will rub you the wrong way a couple miles into your half marathon. Stick with a previously-worn, freshly-washed, seam-free set.

Lace up the pair you’ve been training in lately. If your sneaks are past their prime (running shoes should be replaced every 300 to 500 miles) and your race is three weeks away, it’s safe to buy and break in new ones.

Shorts, capris, or full-length tights? It depends on how warm you like to be. In general, the temperature outside can dictate your leg wear: 35 to 45 degrees Fahrenheit, go for pants; mid-40s to mid-50s, try capris or shorts with knee socks; and slip on shorts for 55 and above. Keep in mind: although most races start early when it’s still chilly, the thermostat will likely rise with the sun, so bare legs might be your best option.

Same deal with bottoms, the temperature and your comfort should dictate which shirt you pull over your head on race day. Sleeveless tops and sports bras, like the one seen here on ultra-runner and Athleta ambassador Julia Stamps Mallon, make a great base layer. Also, look for shirts made with moisture-wicking fabric—it won’t chafe sweaty skin the way cotton can.

Start lines at fall half marathons are notoriously chilly, so keeping your arms covered is a must do. But as you warm up, you’ll probably want to ditch the sleeves. Wear something you can toss to spectators, tuck into a pocket, or tie around your waist.

The ultimate fitness watch, Fitbit Surge can track your distance, splits, and more during training and on race day. Nothing builds confidence more than seeing your progress. Get ready to crush that finish line!