July in Naples

The National Weather Service's Miami office, the forecast office for the Naples zone, says the South Florida wet season usually runs through three phases, and names the one that begins in early July “hottest with intermittent dry periods,” when the subtropical high typically has its greatest influence over Florida and leads to episodes of Saharan dust. The Weather Service's Tampa Bay office, for its own West Central and Southwest Florida area, calls July through early September the phase when its region's rainy season peaks.

July's own climate normals, NOAA's 1991 to 2020 set for Naples Municipal Airport, put its rainfall at 7.77 inches, third in the table behind August's 8.89 and September's 8.60, and its average, high and low at 83.1, 90.8 and 75.5 F, each second only to August's, the month that tops all three temperature columns on August in Naples. The same normals add a provisional average of 16.1 days with at least 0.01 inch of rain, and put the first quartile, median and third quartile of July's nonzero monthly totals at 6.38, 7.52 and 9.64 inches.

By the 15th, NCEI's month-to-date normal has reached 4.00 of July's 7.77 inches, about 51 percent, yet the daily chance of measurable rain, a provisional figure, barely moves across the month, 51.5 to 54.9 percent, a 3.4-point climb against May's 17.0-point climb over its own thirty-one days. Every figure above is a thirty-year average for one airport, never a forecast for any single July.

NWS Miami calls heat a chronic hazard through South Florida's long summer, and says the hottest period is typically July and August, when the maximum daily heat index can frequently reach or exceed 100 F.

The National Weather Service defines the heat index as how hot it really feels once humidity is factored in with the air temperature, and notes that full sunshine can add up to 15 F to that felt heat, since the index assumes shade and light wind. That figure describes a person in the sun, never a roof, a paver or a pane of glass.

NWS Miami's own heat page, with its daily heat index forecast maps, is the route for a given day; the national line it carries is that alert procedures begin when the heat index is expected to exceed 105 to 110 F, depending on local climate, for at least two consecutive days. What a hot afternoon means for work already scheduled is answered on roof cleaning in the summer heat, sealing pavers in the Naples summer heat and cleaning windows in the summer sun.

NOAA's Atlantic Oceanographic and Meteorological Laboratory says Saharan Air Layer activity usually ramps up in mid-June, peaks from late June to mid-August and begins to subside rapidly after mid-August, that the layer can suppress clouds and thunderstorms when it reaches the U.S. coastline, and that during the day the sky takes on a hazy white look. Read side by side, a reading of this page rather than either agency's, AOML's peak and NWS Miami's hottest phase cover the same stretch of summer, and across it, July 1 through August 19, the airport's daily normal high holds between 90.7 and 91.0 F.

NWS Miami's “intermittent dry periods” describes the season, not a schedule for a sealer. ICPI's Tech Spec 5 and SEK-Surebond's site-preparation bulletin each ask for the same thing before most sealers go on, a surface that has gone at least 24 hours without moisture, and SEK-Surebond's weather bulletin adds a second dry span, 24 hours after the coat goes down.

Every day from June 24 through August 31 carries a provisional daily chance of measurable rain at Naples Municipal Airport of 50 percent or higher, so no week of July stands out as drier in the normals by more than a few points. A smoothed average says nothing about how long any real dry spell lasts; the forecast for the next day, never the season, decides a given week.

SEK-Surebond writes that its sealers typically should be applied when day and night temperatures sit between 40 F and 95 F, a window that holds every one of July's daily normals, and never when the surface itself is above 120 F, a reading an airport's air-temperature normal cannot supply. Two Techniseal sheets set narrower tops, 85 F for one product and 30 C, about 86 F, for the other, and the airport's daily normal high is at or above both on every day from April 29 through August 31. The ceiling that governs a given job is printed on the can in use, not on the calendar, and that answer, plus what a shower shortly after the coat goes down does to it, is on what temperature is too hot to seal pavers and how long sealer needs before rain can fall on it.

The National Hurricane Center's Table 1, its average pace for the 1991 to 2020 Atlantic seasons, puts the second named storm by July 17, well ahead of the first hurricane, which the Center's typical-timing line places in early to mid-August (its own table names August 11), adding that formation dates in an individual season could vary considerably from those averages.

NWS Melbourne's monthly lightning climatology for the state, built on ten years of flash-density data from 1986 to 1995, names July the peak month for lightning across Florida, with August still very active and a significant decrease statewide by September; the same page notes a minimum over the south part of the state on nearly all of its monthly maps. Neither line is a Naples ranking.

Once thunder is heard, the National Weather Service's rule is to move at once to safe shelter, which it defines as a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with the windows up, and to stay there “at least 30 minutes after you hear the last sound of thunder”; NWS Miami's Hazardous Weather Outlook carries the day's own lightning danger, from none to high. How that rule falls on a job already underway is on roof cleaning in the rainy season and cleaning a roof while it is raining; what a storm leaves on a roof is a licensed roofing contractor's and an insurer's question, not a calendar's, and the term is defined at hurricane season.