Most standard carbonated soda cans will rupture somewhere above 130 °F (about 55 °C) when heated, though the exact failure point depends on the beverage’s carbonation level, the can’s condition, and whether the heat exposure is sudden or gradual. On the cold end, a can left in a freezer will typically burst once the liquid begins solidifying, generally a few degrees below 32 °F (0 °C). The range is wide enough to matter in everyday life, because a car parked in summer sun or a forgotten six-pack in a deep freezer can easily reach those thresholds.
How Heat Builds Pressure Inside a Sealed Can
A sealed soda can at room temperature already holds a surprising amount of pressure. The dissolved carbon dioxide pushing against the walls produces an internal pressure in the range of 50 to 60 psi, which puts the aluminum shell under a hoop stress of roughly 130 MPa, close to half the material’s yield strength even under normal conditions.1Engineering Fracture Mechanics. A pressure vessel fracture mechanics study of the aluminum beverage can That means the can is already working fairly hard just sitting on a shelf at 72 °F.
When the temperature rises, two things happen simultaneously. First, the CO2 dissolved in the liquid becomes less soluble and escapes into the headspace above the liquid, adding gas pressure. Second, the liquid itself expands slightly. Together, these effects can push internal pressure toward 90 psi under what engineers call “severe service conditions,” such as sitting in a hot warehouse or a sun-baked vehicle.1Engineering Fracture Mechanics. A pressure vessel fracture mechanics study of the aluminum beverage can At that level, the hoop stress in the aluminum wall climbs to about 207 MPa. Push the temperature a bit higher and the pressure exceeds what the can was designed to hold. The weakest point, usually the concave dome at the bottom or the scored pull-tab area on top, gives way first.
The relationship between temperature and pressure inside a sealed carbonated container is roughly linear over the range that matters: every 10 °F of heating adds several psi of internal pressure. Once you cross into the neighborhood of 130–140 °F, the cumulative pressure gain is enough to buckle or rupture a standard 12 oz aluminum can. Cans that are especially carbonated, like certain energy drinks or craft sodas with high CO2 volumes, can reach failure pressure at slightly lower temperatures because they start with higher baseline pressure.
How Hot Does a Parked Car Actually Get
The most common real-world scenario for a soda can explosion is a car left in direct sunlight. People tend to underestimate how hot the interior of a closed car gets. A study measuring cabin temperatures in vehicles parked under full sun in tropical conditions recorded a peak interior temperature of 68.7 °C (about 156 °F) in a sedan, with the larger cabin of an SUV still reaching 59.4 °C (roughly 139 °F).2International Journal of Engineering Materials and Manufacture. Parked Car Interior Temperature Investigation in Brunei Darussalam Those measurements were taken at the dashboard level, where temperatures spike highest due to direct solar radiation through the windshield. A can sitting in a cup holder or on a seat in a sedan exposed to tropical or desert sun is well within the danger zone.
Even in temperate climates, summer car interiors routinely exceed 120 °F (49 °C) within thirty minutes of parking in the sun, and can push past 140 °F (60 °C) on hotter days. A dark-colored dashboard amplifies this further. The takeaway is straightforward: any carbonated can left in a sealed car on a warm, sunny day is at risk. The trunk is slightly cooler than the cabin but not reliably safe either, because trunk temperatures in a sun-soaked car still routinely hit 110–130 °F depending on the vehicle and ambient weather.
This is why the cans usually explode in cars during the afternoon, when interior temperatures peak, rather than in the morning. If you leave sodas in the car, cracking a window helps a little but does not prevent the temperature from climbing well past the comfort zone for a pressurized aluminum container. Parking in shade or using a windshield reflector makes a bigger difference, though neither guarantees the cabin stays below the failure threshold on an extreme day.
When Freezing Causes Cans to Burst
Heat is the more dramatic threat, but freezing accounts for plenty of exploded soda cans too. Water expands by about 9% when it solidifies into ice, and a standard soda can has very little empty headspace to absorb that expansion. Once enough of the liquid freezes, the volume increase pushes outward on the aluminum walls with enormous force while the CO2, already under pressure, gets compressed further. Eventually something gives.
Plain water freezes at 32 °F (0 °C), but soda freezes a bit lower because dissolved sugars depress the freezing point. The higher the sugar concentration, the more the freezing point drops: in aqueous sugar solutions, the depression is roughly proportional to the concentration of dissolved molecules.3Bulletin of the Chemical Society of Japan. The Volumes of Hydrated Glucose, Sucrose and Raffinose Molecules, and the Osmotic Pressures of These Aqueous Saccharide Solutions as Measured by the Freezing-Point-Depression Method A typical regular soda with around 10–12% sugar by weight freezes at roughly 28 °F to 30 °F (-2 to -1 °C). Diet sodas, which contain almost no sugar, freeze closer to 32 °F. That means a diet can left in a freezer will start solidifying sooner than a regular one and is, ironically, more likely to burst first.
Freezing failures tend to be messier than heat failures. When a can bursts from heat, the contents are still liquid and spray outward. When a frozen can cracks, the expanding ice often splits the seam slowly, and you discover the damage only after the slushy mess begins to thaw and leak everywhere. Some cans survive a full freeze if the ice expansion happens to push out the dome at the bottom without fully rupturing the wall, but those cans are structurally compromised and should be discarded.
Diet Soda Versus Regular Soda
You might assume that all soda cans fail at the same temperature, but the contents matter. Sugar affects both the freezing behavior and, to a lesser extent, the CO2 retention of the liquid inside. Regular soda with its heavy sugar load holds CO2 somewhat differently than the artificially sweetened water in a diet can. In practice, though, the carbonation levels are similar enough that heat-related failure temperatures are within a few degrees of each other for both types.
The freezing difference is more meaningful. As noted above, diet soda freezes at a higher temperature because there is almost no dissolved sugar to depress the freezing point. If you forget a mixed case of regular and diet soda in a garage that drops below freezing overnight, the diet cans are the ones most likely to burst. This catches people off guard because they think of diet drinks as “lighter,” but lighter in calories has nothing to do with freeze resistance.
There is also a density difference that matters in a different context: diet cans are slightly less dense than regular cans (water plus artificial sweetener weighs less than water plus sugar), which is why a diet can floats in water while a regular can sinks. This is a fun party trick but has no bearing on explosion risk. What does matter is the total gas volume dissolved in the beverage at filling, which varies by brand and product line more than by diet-versus-regular labeling.
Can Age and Structural Weaknesses
A brand-new can off the production line is at its strongest, and that strength starts to decline almost immediately. Research on the aluminum alloys used in beverage can ends shows a clear time-dependent loss of buckling strength. After a year of storage at room temperature (20 °C), the can end loses about 5% of its structural strength, with roughly half of that drop occurring in the first three to four weeks.4Computer Methods in Materials Science. The influence of aging on buckle strength loss in AA5182-H48 for beverage can ends Store those cans somewhere warmer, say 40 °C (104 °F), like a hot garage or warehouse, and the buckling strength drops by 8% in just four weeks.4Computer Methods in Materials Science. The influence of aging on buckle strength loss in AA5182-H48 for beverage can ends
That might sound like a small percentage, but remember that a can at room temperature is already operating at nearly half its yield stress. A 5–8% reduction in the strength of the weakest structural element means the can will fail at a lower internal pressure than it would have when new. This is why older cans stored in warm conditions are more likely to burst: they are weaker and, if stored warm, also under higher pressure at the same time. The two effects compound. A fresh can might survive a brief stay in a hot car; a year-old can that has been sitting in a warm storage unit is living closer to the edge.
Physical damage also matters. A dent in the sidewall introduces a stress concentration where the metal has been plastically deformed. Even if the dent looks cosmetic, it creates a weak spot where the wall is thinner or the internal coating has cracked. A dented can does not need as much internal pressure to fail as an intact one. If you have a dented can and you plan to transport it in a hot car, you are rolling the dice.
Shaking and Agitation Do Not Change the Failure Temperature
A widespread belief holds that shaking a soda can makes it more likely to explode from heat. This is a misunderstanding of what shaking actually does. When you shake a sealed can, you cause dissolved CO2 to come out of solution and form tiny bubbles, which is why the can spurts when opened. But the total amount of CO2 in the can stays the same whether it is shaken or still. You have not added gas or created pressure from nothing; you have just redistributed it between the dissolved and gaseous phases temporarily.
In a sealed, unopened can, the pressure equalizes quickly. Within a few minutes of sitting still, the bubbles redissolve and the pressure returns to whatever it was before shaking. So a shaken can sitting in a hot car is not at greater risk of bursting than an unshaken one at the same temperature. The danger comes from the temperature, not from whether the can was jostled during transport.
That said, agitation does matter at the moment of failure. If a can is right at the edge of its pressure tolerance and gets knocked around, the physical impact can trigger the rupture. Think of it as the last nudge rather than the root cause. The pressure buildup from heat did the real work; the bump just tipped the balance.
What an Exploding Can Actually Looks Like
When a soda can fails from heat, the most common failure mode is not a dramatic all-at-once detonation. Usually the bottom dome, which is concave to help the can resist internal pressure, “pops” outward first. Engineers call this dome reversal. Once the dome inverts, the can loses its structural geometry and the weakened bottom seam or the pull-tab area gives way, releasing a pressurized jet of sticky, aerated liquid. The spray radius can be surprisingly large: several feet in all directions, enough to coat a car interior, a freezer shelf, or a garage wall.
In rarer cases, particularly when the can has a pre-existing defect or has aged considerably, the sidewall itself can split. This produces a louder pop and a more forceful release. The aluminum edges left behind are sharp enough to cut skin, so cleaning up a burst can calls for some caution. Frozen can failures tend to be quieter, with a slow crack along a seam rather than a violent burst, but the cleanup is just as tedious because the sugary liquid seeps into everything as it thaws.
The sticky residue from a burst soda can is not just annoying; it can damage surfaces. The combination of sugar (or sugar substitutes), phosphoric or citric acid, and caramel coloring in most sodas stains fabric, corrodes some finishes, and attracts insects. If a can explodes in your car, clean it as soon as possible. Warm water works better than cold for dissolving the sugar residue, and you will want to wipe down any metal surfaces to prevent the acid from etching paint or trim.
Altitude and Ambient Pressure
If you live at high altitude or you are driving cans over a mountain pass, the external atmospheric pressure on the can is lower than at sea level. The internal pressure stays the same regardless of elevation, but the pressure differential between inside and outside increases. A can at 50 psi internal pressure in Denver (where atmospheric pressure is roughly 12 psi instead of the sea-level 14.7 psi) has an effective pressure differential about 2–3 psi higher than the same can at the beach. That is not enough on its own to cause a failure, but it narrows the safety margin slightly.
Where altitude becomes more relevant is in combination with heat. If you are driving through the desert Southwest in summer with a case of soda in the back seat, you are dealing with extreme cabin temperatures and slightly reduced external pressure at the same time. Neither factor alone would burst a fresh can, but together, and especially with an older or damaged can, the risk goes up. Hikers and campers sometimes discover this at high-altitude campsites where afternoon temperatures swing sharply: a can left in the sun at 10,000 feet is under slightly more stress than the same can at sea level.
Keeping Your Cans Intact
If you want to transport soda in warm weather, a basic cooler with a few ice packs keeps the cans well below the danger zone indefinitely. No cooler? At minimum, keep the cans on the floor of the vehicle rather than on the dashboard or seats, since floor-level temperatures run 15–25 °F cooler than dashboard level in a parked car. Covering the cans with a towel or jacket provides a small amount of insulation that slows the temperature climb, buying you a couple of extra hours before pressure becomes a concern.
For freezing, the simplest rule is to set a timer if you put cans in the freezer to chill quickly. Most home freezers are set to around 0 °F (-18 °C), well below the freezing point of any soda. A room-temperature can placed in a freezer will reach the liquid’s freezing point in roughly 60 to 90 minutes, depending on the freezer temperature and how many other items are absorbing cold. Pulling the can out after 20 to 30 minutes gives you a nicely chilled drink with no risk of ice formation. Leave it for two hours and you are almost certainly looking at slush, expansion, and a potential rupture.
One option that avoids the problem entirely is switching to plastic bottles for situations where temperature extremes are likely. Plastic bottles flex under pressure rather than shattering, and their screw caps can vent before the container fails catastrophically. The trade-off is that plastic bottles lose carbonation faster over time, but if you are packing drinks for a road trip or leaving them in a cabin during winter, the convenience of not scrubbing soda off your car’s headliner is worth it.