Can a roof be cleaned in the winter?

Before the roof, the season. Measured by NOAA at Naples Municipal Airport, a Naples winter is first the dry stretch of the year and second a mild one.

The four winter months together carry less normal rain than August does alone. January is also the coolest month in the normals: NOAA NCEI puts its normal average at 65.3 F, with a normal high of 74.8 F and a normal low of 55.9 F, against an 83.3 F normal average in August. The full twelve months, rain and temperature side by side, are in the Naples climate normals table.

The National Weather Service's Miami and Tampa Bay offices put the wet season on the same dates, May 15 to October 15, compared under roof cleaning in the rainy season. The drier months outside that rainy season are what the glossary calls the dry season.

What the winter changes is the weather around a roof. The roofing documents describe growth as depending on more than how many inches of rain fall.

ARMA's technical bulletin on roof discoloration says the algae species involved are all transported through the air, and that algae growth occurs to varying degrees in all regions of the U.S. and southern Canada, “especially those subjected to warm, humid conditions.” TRI Alliance's Roof Maintenance Guide places the growth on the dust and organic material that settles on tile rather than on the tile itself, and names what starts it: “With enough cycles of heat, moisture and light, spores start to grow.”

GAF's current bulletin on shingle staining is the most specific about moisture. “Blue-green algae requires moisture and proper temperatures to grow. Dew is the primary moisture source.” It adds that the growth generally appears on the northern exposures of a roof, because they receive less sunlight. Rainfall normals measure what falls in showers and storms; they do not measure dew, which is the source GAF names first. A dry season is a season with less rain, not a season without the moisture GAF describes.

Temperature points the same way. Even January, the coolest month in the normals, averages 65.3 F, so the dry season does not take the warmth out of the growth conditions described under the Naples climate and roof staining. A roof that seems to look worse coming out of an unusually wet winter is a separate question, taken up under why a roof looks worse after a wet winter.

None of this turns the winter into a schedule. The roofing makers and associations read for this answer publish no cleaning interval, seasonal or otherwise, and the answer on frequency on the roof cleaning page sets out what they say instead.

The dry season brings no separate rulebook for washing a roof. It brings different weather to the day the washing happens.

Collier County Ordinance 2015-27, as Collier County 311 publishes it, sets equipment and drainage conditions for washing a roof and names no season, so the rule reads the same in January as in August. A City of Naples address is under the city's own code.

The weather is where the season shows. NWS Miami describes the South Florida summer as a season when showers and thunderstorms are almost a daily occurrence, and the winter as one with less frequent precipitation. A roof solution needs time on the surface before it is rinsed, so fewer showers means fewer chances of rain arriving in the middle of that time.

The storm calendar overlaps only at one end. The National Hurricane Center's Atlantic hurricane season runs from June 1 to November 30, so November is both one of the driest months in the Naples normals and the last month of the official season. How the storm months bear on a roof, and why a cleaning is not storm work, is the subject of cleaning a roof before hurricane season.

Whether the winter is the right time of year overall, weighed against the rest of the calendar, is answered under the right time of year for roof cleaning in Naples. A seasonal home that has stood closed through the wet months raises its own timing question, covered under cleaning a seasonal home before the owners arrive.