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The Best Time of Year to Soft Wash in the Lowcountry

Most soft washing advice online says spring or fall and stops there. Around here, spring shows up under a yellow coat of pine pollen, summer brings roofs that can hit 150°F and afternoon storms several days a week, and winter is mild enough that January can be a perfectly good month to clean a house.

Soft washing cleans with a low-pressure spray and a cleaning solution instead of a pressure washer, which the roofing industry warns is likely to damage shingle roofs. Timing matters because that solution has to sit on the house long enough to kill algae, mildew, and mold, and the weather decides whether it gets that time. Here’s how the calendar plays out in Charleston, Mount Pleasant, Summerville, and Goose Creek.

Contents

The Lowcountry Soft Washing Calendar

These averages come from NOAA’s weather records for Charleston International Airport, 1991 to 2020. The last column is our read on what they mean for washing a house.

If you live inland, the story barely changes. NOAA’s Summerville station runs a degree or two cooler most months, gets almost the same rain each year (52.7 inches vs 52.5 at the airport), and still averages about 22 days at 90°F or above in July. The one real difference is winter mornings, covered in the freeze section below. Homes in Summerville, Goose Creek, Moncks Corner, and other inland towns can use the same calendar.

MonthAvg highAvg rainVerdict
January60°F3.4 inFine on mild, calm days
February64°F3.1 inPollen starting; roofs OK on calm days, but it’s the windiest month
March70°F3.4 inHeavy pollen; siding turns yellow again fast
April77°F3.3 inGood once the pollen clears, usually mid-to-late month
May84°F3.3 inGood, especially mornings
June89°F6.2 inMornings only; afternoon storms begin
July91°F6.6 inWorst month of the year
August90°F7.0 inAlmost as bad as July, plus peak hurricane season
September85°F6.0 inOK, but expect rain delays
October78°F4.3 inGreat from mid-month on
November69°F2.7 inBest month of the year, and the driest
December63°F3.4 inFine on mild, calm days

Mid-October through November is the sweet spot, with November the pick of the year. Late April and May come second. July and August are the months to avoid.

Why Weather Changes the Result

The cleaning solution uses the same active ingredient as household bleach, mixed with water. For shingle roofs, the Asphalt Roofing Manufacturers Association says its bleach-and-water mix should sit for at least 15 minutes but no more than 20 before a gentle rinse. Professionals adjust the mix and timing for each surface and each day’s weather.

Heat is the big one. On a 95°F day, a roof mix can dry on the roof and leave white residue before it’s done working. Bleach also breaks down faster in heat and sunlight, even sitting in the container.

Cold slows things down. Soft washing can happen year round as long as it isn’t at or near freezing, though the solution takes longer to do its job in the cold.

Skip freezing days, hot direct sun, and wind. The best day is gray, still, and mild, when nothing is rushing the solution to dry.

The Best Windows

Mid-October Through November

This is the best stretch of the year. Average highs slide from 78°F in October to 69°F in November, so the solution stays wet long enough to work. November is the driest month of the year at both the airport and the Summerville station. The pollen is long gone, the afternoon storms have stopped, and your shrubs are past some of the most stressful months for landscape plants.

The catch is wind. The area’s breezier season starts in late October (more on that below), so fall washing is a day-by-day call. A calm November morning, once the dew has dried, is close to perfect. A gusty one means rescheduling. Fall is busy, so call in September for an October or November date.

Fall timing also works against mildew. It grows best between about 70°F and 90°F when there’s moisture around, according to a 1999 report in the Journal of Coatings Technology. The Lowcountry spends roughly April through October in or near that range. A fall cleaning clears off the season’s growth just as the weather turns less friendly to it.

Late April Through May

Spring works if you wait out the pine pollen. It usually clears by mid-to-late April. After that, it’s still mild and the heavy summer rain hasn’t started. May averages under five days at 90°F or above.

When to Hold Off

Peak Pine Pollen

Loblolly pine makes up nearly half the trees in South Carolina, and it’s behind the yellow haze that settles over the Lowcountry every late winter and spring. Some trees start releasing pollen as early as late January, with pine and oak following later in spring, and the timing shifts every year.

Wash your siding in early March and there’s a good chance it’s yellow again within a couple of weeks. You’ll have paid to clean it twice. Go by what you see: when a rinsed car or deck stays clean for a few days, the worst has passed.

Soft washing isn’t a fix for pine dust, though. Pollen season is just something to plan around so a wash doesn’t get wasted. The cleaning solution is meant for algae, mildew, and mold. If the yellow film is your main concern, a plain water rinse or another cleaning method is the better fit.

July and August Afternoons

This is the worst time to soft wash in the Lowcountry. July averages 21 days at or above 90°F, and a dark shingle roof on a sunny summer day can get up to 150°F. On a surface that hot, the solution dries before it finishes working, and what’s left can streak.

Then there’s the rain. June through September delivers close to half the year’s total, at the airport and in Summerville alike, much of it from afternoon storms set off by the sea breeze. A storm that hits while the solution is still working washes it off before it’s done.

Freezing and Near-Freezing Days

At the airport, the last spring freeze typically comes around March 7 and the first fall freeze around November 27, per NOAA’s records. Inland runs colder. The Summerville station averages about 45 nights a year at or below freezing, roughly double the airport’s 22, with the last spring freeze around March 22 and the first fall freeze around November 12. NOAA doesn’t track temperatures in Goose Creek itself, but the town sits between the airport and the Moncks Corner station, which averages about 32 freeze nights a year, so expect something in that range. Near the water it’s milder: downtown Charleston averages about 6 freeze nights a year and Sullivan’s Island about 18. On a freezing morning, rinse water can ice over walkways and steps, and water that soaks into brick or stucco can freeze and expand. Most Lowcountry winter afternoons are well above freezing.

Windy Days

Wind blows the spray where it shouldn’t go, like onto your car or the neighbor’s azaleas. The area’s windier stretch runs from late October to early May, peaking in February. Plenty of mornings in that stretch are still calm, so check the wind the morning of the wash. A good crew should reschedule a blustery day rather than push through it.

When a Storm Is on the Way

Hurricane season runs June 1 through November 30. On average, activity peaks around September 10. Washing in those months is fine on a clear day, but don’t clean the house the week a tropical storm is forecast to dump debris, pine straw, and several inches of rain on it. Let it pass, then clean up what it left. Coastal homes also pick up a salt film from ocean breezes year round, which is covered in the guide to the salt air problem on coastal SC homes.

Not sure where your house falls on this calendar? Find A Provider who knows how Lowcountry weather affects the job.

Roofs and Siding Don’t Share a Calendar

Heat is a bigger problem on a roof than on siding. On siding, the crew can move to the shady side of the house as the sun comes around. A roof has far less shade. Cleaning can also make a roof slippery, and ARMA recommends that only trained professionals walk or work on a roof at all.

That makes fall and mild, calm winter days a good fit for roof cleaning. Pollen matters less up there, since a yellow tint on shingles fades with the next few rains. The real trouble is the black streaks from roof algae, which ARMA says are most widespread in the Gulf States and along the East Coast, so a Lowcountry roof fights them every year no matter when it’s cleaned.

Siding is more sensitive to pollen. A spring siding wash should wait for the yellow to clear, while a roof can go ahead on a calm February day, if you can find one in the windiest month. Mildew also tends to collect on walls shaded by trees and shrubs where air doesn’t move, according to Purdue Extension, so the side of the house facing the live oaks usually needs the most attention.

If It Can’t Wait Until Fall

Sometimes you don’t get to pick. Say a Summerville homeowner gets an HOA notice about green siding in late June. A good crew should start early, once the morning dew has dried but before the sun heats the walls, and work around the house to stay ahead of it. They should soak your shrubs and beds with plain water before any cleaning solution goes down, which cuts down on how much the plants absorb, then rinse everything again afterward. On a hot day, they should also adjust how strong the mix is and watch the radar for the afternoon storm. On your end, turn off the sprinklers that day so they don’t water down the solution while it’s working.

Ask about those steps when you get a quote for summer work. If a crew can’t tell you how it handles heat, pass.

Frequently Asked Questions

Is it better to soft wash in the spring or the fall?

In the Lowcountry, fall. October and November are mild, dry, and pollen-free. Spring works too, but only after the pine pollen clears, which in a typical year means mid-to-late April.

Can you soft wash in the winter in the Lowcountry?

Yes, on mild, calm days above freezing. Average January highs run about 58°F in Summerville and 60°F at the airport, warm enough for the cleaning solution to work, though it works slower than on a warm fall day. Skip any morning with a hard freeze in the forecast, and if you’re inland, let the day warm up before the crew starts.

What happens if it rains after soft washing?

Rain while the solution is still working (15 to 20 minutes for ARMA’s basic bleach mix on a shingle roof; professional mixes and other surfaces vary) washes it off early and can leave the job unfinished. Rain after the house has been treated and rinsed doesn’t hurt anything.

Will soft washing kill my plants in the summer?

Soaking plants with plain water first, keeping runoff under control, and rinsing everything afterward protects most landscaping. Summer is still the riskiest season for your beds, since hot, dry summer stretches are some of the most stressful times for plants and a shrub already wilting in July heat has less room to handle a mistake.

Find a Soft Washing Professional in the Lowcountry

Pick the month, then pick a crew that watches the forecast as closely as it watches your flower beds. Contact us and we’ll get you sorted.

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