January in Naples

NCEI's 1991 to 2020 normals give Naples Municipal Airport a 6.0 percent probability of at least one night at or below 32 F in a given year, and 32.6 percent for a night at or below 36 F; for January alone the figures read 4.9 and 21.6 percent, and the airport averages 0.1 day a year at or below 32 F.

At the 10, 50 and 90 percent probability levels, the same normals give no first or last 32 F date for the airport: each of those six fields reads as insufficient values to perform the computation, in NCEI's own flag. NCEI's documentation lists further probability levels for those dates, not read for this page, so the gap is stated for those six fields only.

NWS Miami's Cold Weather Hazards page says that overnight temperatures “rarely drop below freezing in South Florida, especially along the coasts,” and that “Inland areas are more susceptible to below freezing temperatures, primarily during the middle part of January.” On frost, the same page says: “With adequate low level moisture and calm wind, frost may occur at temperatures as warm as the mid 30s.” The National Weather Service defines a freeze as the surface air temperature expected at or below 32 F over a widespread area for a climatologically significant period, and a hard freeze as 28 F or lower for an extended period, killing most types of vegetation.

NCEI's own figure is a probability: 4.9 percent for the month, not a zero and not a certainty.

January's own four normals are 1.68 inches of rain, a 65.3 F average, a 74.8 F normal high and a 55.9 F normal low. Of the twelve months in the Naples climate normals table, January's average, high and low are each the lowest, a comparison whether Naples exteriors need more care than homes up north puts beside a colder climate.

That 55.9 F normal low is an average of thirty Januaries' monthly averaged lows, adjusted and filled the way NCEI describes, not the coldest night of any January; the nights NCEI actually counts are in the next section, and what a climate normal is and is not is set out under that term.

Inside the month, NCEI's daily normals put the lowest point of the year's own smoothed minimum at 55.5 F, running from January 16 through January 21. That is where a thirty-year average happens to bottom out, not a forecast for those particular days and not a label for the coldest week of any real January.

January also carries more rain than November, December or February, the other three of the four driest months: 1.68 inches against 1.39, 1.32 and 1.40, with 4.7 provisional days of at least 0.01 inch, the most of any month from November through March. The middle half of January's nonzero monthly totals runs 0.54 to 2.44 inches, and about 36 percent of the month's rain has typically fallen by the 15th in NCEI's month-to-date normals, 0.61 of 1.68 inches, leaving the larger share for the back half of the month.

NCEI's 1991 to 2020 normals give January, on average, 20.6 nights at or below 60 F, 9.1 at or below 50 F and 1.7 at or below 40 F at Naples Municipal Airport, each the most of any month, plus 0.1 night at or below 32 F and a 4.9 percent probability of at least one such night in the month. The cool season's first nonzero readings at the 40 F count and the 36 F probability arrive a month earlier, on December in Naples.

Set against the makers' own lines, as reasoning and not as any maker's sentence: Techniseal's NS sheet holds its 50 F to 85 F window through the application and the 24 hours after it, so the night after a daytime job counts, and NCEI puts 9.1 January nights at or below 50 F; SEK-Surebond's TB17 puts its typical range at 40 F to 95 F for both day and night temperatures, with no application on a frozen surface, against 1.7 January nights at or below 40 F; Seal 'n Lock's Super-Wet-Look guide says “Do not apply if surface or ambient temperature is below 50°F,” names 60 F to 90 F for best results, and carries a line on curing before a freezing night that cure time owns. NCEI measures air at the airport, not a paver's surface, and none of these counts is the number of nights that break a label; which window governs a given night is the product in hand, weighed at sealing pavers in a Naples winter.

January's mornings bring the two kinds of moisture the National Weather Service defines separately: dew, “Moisture that has condensed on objects near the ground, whose temperatures have fallen below the dewpoint temperature,” and fog, water droplets suspended in the air at the surface, which is not a wet surface. NWS Miami puts the main period for fog formation in South Florida from late fall to early spring, and says that when fog forms there it typically forms over the Everglades and along the southwest coast of Florida.

Read together, as reasoning: ICPI's sealer condition asks for a surface free of moisture or surface dampness, and dew, by NWS's definition, can put that dampness on a roof or a paver on a cool January morning even with only 4.7 provisional days of measurable rain in the month. Fog is suspended droplets, and no source read for this page says fog wets a surface the way dew does. A sealer over a dew-covered surface is taken up at what happens if sealer goes on wet pavers, and a foggy pane at can foggy windows be cleaned.

For a roof, ARMA ties algae growth to warm, humid conditions, and GAF's bulletin names dew as the primary moisture source; neither names a temperature or a season at which growth stops, so this page says neither that January slows the organism nor that it does not. The roof's winter question is the subject of can a roof be cleaned in the winter.

UF/IFAS's Gardening Solutions page puts Florida trees' pollen release at January to June, so the statewide window opens in January; the full calendar, oak peaks included, is at pollen season.