Once you've ruled out the flimsy stuff, look at performance consistency. Heat can make e-liquid thinner, which means it might flood the coil or mute the flavor. A good disposable will have a stable draw—not too airy, not too tight—and the flavor should stay clear from the first hit to the last.

Here's a practical test: if you're in a store, ask if you can feel the draw. Many shops have test units. If you can't, look for devices with adjustable airflow. That's a sign the manufacturer thought about different conditions. Also, consider the e-liquid ratio: higher VG (vegetable glycerin) tends to be thicker and handle heat better, but it also produces more vapor. If you prefer a stronger throat hit, PG (propylene glycol) is thinner but more prone to leaking in heat. Most disposables use a balanced mix, but it's worth asking the shop staff.

Battery life is another factor. In heat, batteries work harder. A device that lasts two days in moderate weather might only last one and a half in a heatwave. Compare the stated battery capacity (usually in mAh) but know that real-world performance varies. Look for brands that mention overheat protection—that's a sign they've tested for summer conditions.