Can you make sun tea on an overcast day?

The allure of sun tea—that perfectly steeped, slightly sweeter brew achieved solely by the sun's gentle warmth—is a quintessential summer ritual for many. It conjures images of pitchers sweating on porches while the day bakes down. Yet, the transition from brilliant sunshine to a thick, grey blanket overhead brings a common question for the dedicated tea drinker: can you still make sun tea when the sun decides to take a vacation? The simple answer is yes, but the success of that brew hinges less on the sun itself and more on the temperature the water reaches and how long it stays there.

This method of brewing, which avoids the harsh rapid heating of boiling water, relies on lower, sustained temperatures to extract the flavor compounds from the tea leaves. ^[6][9] When that direct, powerful solar radiation is blocked by clouds, the primary engine for heating the water stalls, forcing us to reconsider the timing and, most importantly, the safety of the resulting beverage. ^[5]

# Brewing Heat

Sun tea works because the combination of sunlight and ambient warmth slowly coaxes the flavor components out of tea leaves, often resulting in a less bitter final product than boiling water can produce. ^[6][9] Standard sun tea recipes usually call for placing the pitcher outside for three to five hours on a very hot, sunny day. ^[3] The ideal temperature range for steeping is generally around $130^\circ\text{F}$ to $175^\circ\text{F}$ for optimal flavor extraction, though different teas have different preferences. ^[5]

However, the moment the sky clouds over, those ideal temperatures become elusive. While sunlight is often cited as the key ingredient, it is actually the heat generated by the sun that does the heavy lifting in the infusion process. ^[9] A fully overcast day drastically reduces the radiant energy hitting the glass pitcher, meaning the water temperature will likely hover near the ambient air temperature, which might be significantly lower than the desired steeping heat. ^[3]

Some enthusiasts argue that as long as the water is warmer than room temperature, some level of extraction is occurring, even if it is slow. ^[4] Others suggest that if the temperature is too low, you are simply creating an environment ripe for microbial growth without achieving proper flavor infusion—a classic trade-off in the sun tea debate. ^[5]

# Cloud Cover Impact

When a day is heavily overcast, the experience shifts from true "sun tea" to what might be more accurately called "warm water infusion" or simply a long, slow cold brew. Brewing time must be drastically adjusted when direct sun is absent. On a bright, hot summer day, a black tea might be perfectly steeped in four hours. ^[3] Under thick cloud cover, that same pitcher might need to sit out for eight, ten, or even twelve hours to achieve comparable strength, assuming the ambient temperature is still reasonably warm, perhaps above $75^\circ\text{F}$. ^[9]

One perspective shared in online communities suggests that if the temperature outside doesn't feel warm to the touch—if you wouldn't be comfortable sitting outside for hours in just a t-shirt—then the water inside your pitcher is likely too cool to properly steep the tea or to reliably kill any lurking bacteria. ^[2] The water simply won't get hot enough to mimic a gentle stovetop warming, which is often cited as a safer low-heat alternative to a rolling boil. ^[7]

A common comparison made among sun tea veterans is that a pitcher left out during a moderately sunny day might achieve the strength of a five-minute steep, whereas the same pitcher on a day where the clouds are thick and unbroken might equate to a two-hour cold steep in the refrigerator, yielding a lighter, less oxidized flavor profile. ^[4][9]

Can you make sun tea in the shade?

# Safety Considerations

The most significant concern surrounding sun tea, particularly on cloudy days, is food safety. The method inherently involves leaving water and tea bags exposed to ambient temperatures for long periods, which can fall squarely into the temperature "danger zone" for bacterial multiplication. ^[5]

The general guidance from health organizations often centers on the fact that temperatures between $40^\circ\text{F}$ and $140^\circ\text{F}$ allow bacteria like Bacillus cereus—which is naturally present in soil and sometimes on tea leaves—to thrive. ^[1][5] A field test conducted by an individual noted that even on a sunny day, temperatures inside a clear glass pitcher often only reached about $130^\circ\text{F}$ to $140^\circ\text{F}$ after several hours, which is near the threshold for killing bacteria but well within the zone where some organisms multiply rapidly. ^[1]

If the day is overcast, the temperature inside the pitcher might never climb above $100^\circ\text{F}$ or $110^\circ\text{F}$. ^[5] When this happens, the flavor extraction is weak, and the safety margin disappears entirely. If you are aiming for a true sun tea flavor profile on a cloudy day, you are fighting a losing battle against temperature, and this is where many safety experts advise against the practice altogether unless a specific, verifiable temperature is achieved. ^[1]

For those who insist on brewing outdoors even when the sun hides, an important mental check is needed: if the ambient temperature is below $70^\circ\text{F}$ to $75^\circ\text{F}$, the risk of inadequate brewing temperature skyrockets, regardless of how long the tea sits. ^[2] It is less about seeing the sun and more about the actual thermal energy available in the environment.

# Alternative Brewing

When the sky is determined to remain grey, the best practice shifts away from the porch and toward controlled environments. If you have already committed your tea bags or loose leaf to the jar, the safest immediate step is to bring the pitcher indoors and finish the brew using refrigeration, effectively turning it into a cold brew. ^[7]

Cold brewing is an excellent, zero-risk alternative to sun tea. It requires significantly more time—typically 8 to 12 hours, sometimes overnight—but it yields an incredibly smooth, sweet tea because the cooler water extracts fewer of the bitter tannins. ^[7] If your cloudy day turns into a cloudy night, the refrigerator is your friend.

Another indoor technique that mimics the low-and-slow approach is the stovetop steep. While this uses energy, it provides control. Instead of boiling, one can gently heat the water on the stove to just below simmering—around $175^\circ\text{F}$—pour it over the tea, and let it sit, covered, for the usual brewing time, perhaps three to five minutes, before chilling it rapidly. ^[6] This method bypasses the ambient temperature gamble entirely.

For those aiming to replicate the experience of sun tea when the weather fails, try this: place your tea in the glass pitcher and set it on a dark-colored surface inside a closed car parked in a shaded spot for a few hours, then move it to a sunny spot if available, or simply finish it indoors. ^[2] A car parked in shade can still trap more latent heat than an open porch, offering a slight boost over ambient air temperature without the risk of direct sun scorching the leaves.

Why did people stop making sun tea?

# Cloudy Day Tactics

If the forecast is patchy clouds with occasional sun breaks, you might still achieve decent results by being tactical about placement and timing. It's crucial to understand that a light haze might only slightly extend your brewing time, perhaps adding an hour or two to the standard sunny-day recipe. ^[9] A day where the sun disappears completely for hours, however, requires a different strategy.

When brewing on a day that alternates between sun and clouds, always err on the side of caution regarding infusion time. If you typically brew for four hours, push it to six or seven, but always taste it as you go. ^[3] The moment the flavor reaches your preferred strength, stop the infusion, regardless of the time elapsed or the weather conditions. Leaving it out longer on a cool, overcast day only increases the time spent in the flavor-neutral, bacteria-friendly temperature zone.

Here is a simple guideline to help determine if your cloudy day brew is worth the wait, based on general tea brewing principles adapted for low heat:

One helpful analysis focuses on the container material. While clear glass is traditional, a slightly darker or even opaque container placed in direct sun will absorb more radiant heat than clear glass, potentially increasing the internal temperature by several degrees, which can be a game-changer on a mildly overcast day. ^[4] If you must use a glass jar on a grey day, consider wrapping the lower half in aluminum foil to trap and reflect what little solar energy is available, similar to how a solar oven works, directing energy inward rather than allowing it to escape through the sides. This small increase in thermal retention might be enough to push the water out of the bacterial risk zone during peak daytime hours. ^[2]

Ultimately, making sun tea on an overcast day is a balance of patience and pragmatism. If your goal is flavor and speed, the clouds mean you should switch to a different method. If your goal is the ritual and you accept that the flavor will be lighter—more akin to a very long steep—then it can be done, provided you manage the total time to prevent the cool brew from sitting too long before chilling. Trust your senses on flavor, but trust thermometers (or the avoidance of brewing in cool weather) on safety.