How hot and wet is the air a Venice lanai ceiling lives in?

Three public tables, read together: what the weather does, what the humidity does, and what wood does in response.

How hot and wet is Venice, month by month?

The official 1991–2020 normals for the Venice cooperative station put the yearly mean at 73.7°F, with an 83.2°F average high and a 64.2°F average low^{[1] [2]}. The station sits at 8 feet of elevation^[2].

June through September bring 30.70 inches between them, about 60% of the year’s 51.27 inches^[1] (our arithmetic from the table). Those are the months an outdoor ceiling is tested hardest. Cooling degree days add up to 3,621 a year against 418 heating degree days^[1], a reminder that a covered lanai is a warm place most of the year.

How humid is the air under a lanai roof?

Venice has no humidity series in the state table, so we list the two nearest long-record stations, Fort Myers and Tampa. Mornings average 82–91% across the year; afternoons drop to 47–64%^[3].

What does that air do to wood?

Wood trades water with the air until it reaches an equilibrium moisture content (EMC) set by temperature and relative humidity. The USDA Wood Handbook tabulates that equilibrium and says the values may be applied to wood of any species for most practical purposes^[4]. Using that table, we estimated the EMC each month would produce if the wood fully caught up with the air: morning values pair the Venice normal low with the average morning humidity of the two stations, afternoon values pair the normal high with afternoon humidity.

Read this as a range, not a reading. Boards under a roof do not fully catch up with each morning and afternoon, so a real ceiling settles between the columns. The point is the size of the swing: on paper the air alone can swing wood by roughly 8 to 9.5 points of moisture content between morning and afternoon, in every month. Gaps, back-sealing and a finish that lets wood breathe exist because of that swing.

How far a board moves for a given change depends on the species and the cut; tangential shrinkage from green to oven-dry runs from 5.0% for western redcedar to 7.6% for coast Douglas-fir^[4]. The species ledger lists them.