The short answer on when to pressure wash a house in St. Petersburg: once a year, on the shoulder of the rainy season, in late spring or early fall. But “once a year” is the generic national answer, and it understates what a Pinellas County home actually needs.
St. Pete sits in a warm, humid subtropical climate where mildew, mold, and roof algae build up faster than they do almost anywhere else in the country.[2] That changes both how often you wash each surface and when you schedule it. Here’s the schedule we recommend to our own residential customers, with the weather reason behind each number.
Why St. Pete homes get dirty faster than most
Two things drive exterior grime in Pinellas County: heat and moisture.
The National Weather Service defines our rainy season as running from May 25 to October 10 for West Central Florida, with daily thunderstorms peaking from June through September.[1] During those months, afternoon storms leave siding, walkways, and pool decks wet for hours, and the tropical climate pushes moisture and heat into every shaded surface.
That heat-plus-moisture combination is exactly what mildew and mold need. UF/IFAS puts it plainly: “Florida is warm and humid. Pests and organisms, such as mildew and bacteria, may attack organic materials,” and the summer heat and humidity drive mildew and mold-spore growth on and around the home.[2]
In practice, that means a north-facing wall, a shaded walkway, or the underside of a lanai screen that stays damp will grow a green or black film in a matter of weeks, not months, during summer.
When to pressure wash a house: the short answer
Aim for once a year, in one of two windows:
- Late spring (April–May), before the daily storms start. You clear off the dry-season pollen, dust, and salt film so the house starts the rainy season clean.
- Early fall (October–November), after the rainy season tapers off. This removes a summer’s worth of mildew and algae before it has all winter to bake in.
If you only schedule one wash a year, pick the fall. It clears the worst of the summer growth, which is the biggest driver of long-term staining in Pinellas County.
Homes with heavy tree cover, a north-facing elevation, or that sit within a few blocks of the water (salt spray and constant humidity) often need twice a year. Watch the surface, not just the calendar, as covered below.
How often to pressure wash each surface
Different surfaces around a St. Pete home collect grime at different rates. Here’s a practical per-surface schedule:
- House exterior (vinyl, stucco, hardie, painted wood): once a year. Mildew is the main culprit here, and it feeds on the moisture the rainy season brings.[2]
- Driveway and garage pad: once a year, or twice if you park over it daily and it picks up oil, tire marks, and algae in the shade. Concrete in Pinellas grows a dark green film fast.
- Sidewalks and walkways: once or twice a year. These are the slipperiest surfaces when algae coats them, and they stay damp under sprinklers and afternoon storms.
- Pool deck and paver patio: twice a year. Pool splash-out plus humidity makes these the fastest-greening surfaces on the property.
- Roof (soft wash, not pressure wash): every 1–2 years, or when black streaks become visible. See below.
- Fence and screen enclosure: every 1–2 years. Vinyl and aluminum cages hold algae in the joints and screen weave.
If this feels like a lot, it’s the Florida-specific reality; a surface that would go two years between washes in a dry climate needs attention every year here.[2]
The roof is the exception: soft wash, never pressure wash
Roofs deserve their own rule, and it’s the one place you should not reach for a pressure washer.
The black streaks you see on shingle roofs across Pinellas are not dirt; they’re a blue-green algae called gloeocapsa magma, which thrives precisely in the humid, coastal conditions St. Pete has.[3] Asphalt shingle manufacturers are explicit about how to handle it: apply a diluted bleach-and-water solution and rinse with low pressure. Their guidance is blunt: “Never use a pressure washer to clean an asphalt shingle roof as this will cause granule loss and very likely premature failure of the roof system.”[3]
That’s why roof cleaning is a soft wash job, not a pressure washing job. The algae itself doesn’t structurally damage the shingles, but it does ruin the look of the roof and, over time, the curb appeal of the whole house.[3] If you want the full rundown on pressures and methods, see our pressure washing vs soft washing guide.
Signs it’s time to wash (ignore the calendar)
Between scheduled washes, let the surface tell you. Schedule a wash when you notice:
- Green or black film on the north side of the house, under eaves, or on shaded walkways.
- Slippery concrete around the pool or patio; algae is the usual cause after the rainy season.
- Dark streaks running down the roof plane, which is gloeocapsa magma algae and a soft-wash candidate.[3]
- Dust, pollen, or salt haze coating the siding after a dry spell or a windy stretch off the water.
Catching these early keeps a once-a-year wash from becoming a strip-and-restore job later.
When to DIY vs. hire
Pressure washing a driveway or sidewalk is a reasonable weekend job with a consumer-grade electric unit. But the higher the surface, the faster the risks stack up:
- House exteriors involve ladders, reach, and the right PSI for your siding; too much pressure etches stucco and blows water under vinyl.
- Roofs are a soft-wash job with bleach-based chemicals and a ladder, not something to learn on your own roof.[3]
If you’d rather not climb a ladder with a wand, a local crew can knock out the whole exterior schedule in a single visit. For what a full wash costs in St. Pete, see how much pressure washing costs in St. Petersburg and our driveway cost guide.
Frequently asked questions
How often should I pressure wash my house in Florida?
Once a year at minimum, and twice a year if the home is shaded, near the water, or has a north-facing elevation. Florida’s warm, humid climate means mildew and mold grow on exterior surfaces far faster than in drier regions.[2]
What time of year is best to pressure wash a house in St. Pete?
Late spring (April–May) or early fall (October–November). Schedule around the rainy season, which the National Weather Service defines as May 25 to October 10 for West Central Florida.[1]
Do I really need to wash my roof every year?
Not necessarily; every 1–2 years, or whenever black algae streaks become visible. The algae (gloeocapsa magma) is cosmetic rather than structural, but a roof should be soft washed with low pressure, never pressure washed.[3]
Can pressure washing damage my siding or roof?
Yes. Too much pressure can etch stucco, force water behind vinyl siding, and on an asphalt shingle roof strip granules and cause premature failure, which is why manufacturers explicitly warn against pressure washing shingles.[3]
Should I pressure wash before or after the rainy season?
If you’re doing one wash a year, do it after, in early fall, to remove the mildew and algae that accumulated over the summer. A second spring wash is a nice-to-have for removing pollen and salt before the storms return.
Is it worth hiring a pro instead of DIY?
For driveways and walkways, DIY is fine. For the house exterior and roof, anything involving a ladder, reach, or the right PSI for your surfaces, hiring a pro is cheaper than repairing the damage a wrong setting or a fall can cause.
The bottom line
Mark your calendar for the two shoulder windows, late spring and early fall, and let the surface, not the calendar, tell you if you need a mid-year touch-up. In Pinellas County, a once-a-year exterior wash plus an every-couple-years roof soft wash is the minimum that keeps algae, mildew, and salt from winning.
Need a hand scheduling it? We wash driveways, sidewalks, pool decks, house exteriors, and soft-wash roofs across St. Pete and Pinellas County. Get a free estimate, or if you want the DIY route, start with our house pressure washing tips before you pull the trigger on a wand.
This article is general maintenance guidance, not a warranty or professional assessment. Roof cleaning and ladder work carry real risk; when in doubt, hire a licensed, insured contractor.
Sources
[1] https://www.weather.gov/tbw/rainyseason
[2] https://ask.ifas.ufl.edu/publication/HE887
[3] https://www.asphaltroofing.org/algae-moss-prevention-cleaning-asphalt-roofing-systems