Tyler runs an annual average of 47.66 in relative humidity with a dew point of 93.1 / 38.5 °F. Hold 45–55% summer, 30–40% winter indoors and the rest of this page is how.
- Annual rainfall
- 47.66 in
- July high / January low
- 93.1 / 38.5 °F
- Days above 90 °F
- 91
- Humidity normals
- not published for this station
- Indoor target
- 45–55% summer, 30–40% winter
The climate, in numbers that matter to a building
Tyler has a humid subtropical climate, and the number that separates it from the rest of North and Central Texas is rainfall: 47.66 inches a year, close to Houston’s figure and well above the 34 to 39 inches of the Metroplex. The ground around an East Texas house is wet for much of the year, and the air above it reflects that.
The station does not publish a relative humidity normal, so this guide does not quote one. What can be said honestly is that the region sits between Dallas and Houston in air moisture, closer to the coast in summer than the rainfall gap alone would suggest, and that dew points climb into the seventies during Gulf pushes.
The winter is genuine. An average January low of 38.5 °F with hard freezes each year — and a record of −6 °F set in February 2021 — means the cold-climate problem set applies here as much as the humid one. Ninety-one days a year above 90 °F give a long cooling season on the other side of it.
Through the year in Tyler
| Season | What the outdoor air does | What that does to a house here |
|---|---|---|
| Spring | Wet and stormy, with heavy rain, hail and tornado risk | The wettest ground of the year; drainage and roof water matter most now |
| Summer | Hot and humid, with dew points climbing during Gulf pushes | Cooling load with a real moisture component; shaded north walls stay damp |
| Fall | A second rainfall peak followed by drying air | The best ventilation window; time to deal with what summer produced |
| Winter | Cold with hard freezes; occasional severe cold events | Window condensation and dry indoor air, exactly as in North Texas |
What this climate does to a house here
The problems below are the ones that turn up repeatedly in Tyler specifically, rather than the general list.
-
Shade that stops anything drying out
The Piney Woods keep roofs, north walls, crawl spaces and decks in permanent shade. The same construction in open country dries within hours of rain; here it can stay damp for days, which is more than enough time for growth to establish on siding, roofing and anything organic underneath.
-
Crawl spaces under older housing
East Texas has a substantial stock of pier-and-beam houses over vented crawl spaces. In a climate this wet, summer venting draws humid air onto cool joists and encourages exactly what the vents were supposed to prevent — and the shade means the space never gets a drying spell.
-
Both mold and window condensation in one year
Summer brings humid air onto air-conditioned surfaces; winter brings freezes onto glass in rooms that are producing moisture. A house here can grow mold in August and run with water on every pane in January, and the two need opposite strategies.
-
Roof and gutter failures hidden by tree cover
Overhanging trees fill gutters with needles and leaves faster than in open country, and the resulting overflow soaks walls and foundations. It is the most common cause of penetrating damp locally and one of the cheapest to prevent.
-
Severe cold events the housing was not built for
The February 2021 event took the region to −6 °F. Housing built for a mild winter loses heat fast in those conditions, surfaces drop far below the dew point, and pipes in unconditioned spaces freeze. It is rare and it is worth having a plan for.
What is your reading telling you?
- Dew point
- 53 °F
- Mold risk, cold walls
- Moderate
Still inside the accepted range, but this is where cold surfaces begin to sweat.
Every fix that works here, cheapest first
The complete ladder for a Tyler house, with both seasons covered. More of the work here is outdoors than in any other guide in this branch, because the shade and the rainfall are what set the conditions.
Ventilate in spring, fall and cold weather
For much of the year the outdoor dew point sits below the indoor one, and twenty minutes of cross-ventilation twice a day removes more water than any machine. Check the dew point during humid summer spells and skip it then.
Clear gutters more often than the manual says
Tree cover fills them several times faster than in open country. Overflowing gutters soak walls and foundations, and this is both the commonest local cause of damp and the cheapest to prevent.
Cut winter moisture production during freezes
Every pint you put into the air during a cold snap lands on the coldest glass in the house. Fan on for showers, lids on pans, dryer vented outside, no laundry drying indoors until it breaks.
Cut back growth touching the building
Branches and shrubs against walls and roofs hold moisture directly against the fabric and block what little drying air reaches those surfaces. A clearance of a couple of feet does more for a shaded north wall than any coating.
Seal the attic air paths before winter
Weatherstrip the hatch, seal around light fittings and pipe penetrations, and confirm bathroom ducts terminate outside. This is the direct fix for winter attic condensation and it costs very little.
A dehumidifier for summer, and for the crawl space
A 30 to 50 pint unit under the 2019 rating for the house, and a small dedicated unit for an encapsulated crawl space. In this climate the crawl space is frequently the single largest moisture source in the building.
A humidifier with a humidistat for winter
Set it to 35 to 40% and use the glass as the check. Freezes here are cold enough that a house can run into the twenties, which gaps floors and irritates airways.
An ERV for a tight house
It moderates moisture in both directions, which is what a climate with both problems needs. An HRV works on heat alone and will make a winter house drier still.
Encapsulate the crawl space, then insulate and glaze
A sealed ground cover with a small dehumidifier is the durable answer under a pier-and-beam house here — venting it in a wet shaded climate pulls humid air onto cool joists. Then raise the surface temperatures that decide winter condensation: insulation, better glazing, insulated reveals.
Local construction, and why it changes the answer
East Texas housing spans a wide range of eras, and the older pier-and-beam stock is where most of the serious moisture damage occurs. A vented crawl space under a shaded house in a 48-inch rainfall climate is a reliable way to keep joist ends damp for years, and the failure is slow enough that it is usually discovered during unrelated work.
Tree cover is the local variable that most changes outcomes. It reduces cooling load substantially, which is a real benefit, and it costs you the drying that sun and wind would otherwise provide. The practical compromise is clearance rather than removal: keeping branches off the roof and walls, and keeping the ground immediately around the building clear enough for air to move.
Because the region has both problems, the most useful instrument here is a hygrometer left in place all year. A house managed correctly in August is frequently mismanaged in January, and the two sets of symptoms — mold on a wall, water on a window — are rarely recognized as the same subject.
Common questions
Is East Texas as humid as Houston?
Close, in rainfall — 47.66 inches at Tyler against roughly 50 in Houston — and somewhat less so in air moisture, because Tyler is far enough inland that Gulf dew points arrive in pushes rather than continuously. The important difference is the winter: Houston barely has one, and Tyler has hard freezes every year, which gives an East Texas house a whole problem set the coast does not deal with.
Why is the north side of my house always green and damp?
Because it gets no direct sun and, under tree cover, very little drying wind either. Algae and mildew on siding are a moisture symptom rather than a cleaning failure — the surface is simply wet for far more hours a year than the sunny elevations. Clearing branches back to let air move does more than repeated washing.
Should crawl space vents be open in an East Texas summer?
Current building science says no in this climate. Summer venting draws warm humid air into a cool space and condenses it on the joists and the underside of the floor, which is the opposite of what the vents were intended to do. Encapsulation — a sealed ground cover, sealed vents and a small dehumidifier — is the durable answer under a shaded house in a wet region.
What should I do about a severe freeze like February 2021?
Treat it as a heating and plumbing event first and a humidity event second. Keep interior doors open so heat reaches exterior walls and pipe runs, let a faucet drip on the most exposed line, and drop the indoor humidity target for the duration — during an event that cold, even 30% will condense and freeze on ordinary glass, and the meltwater afterwards does the damage.
Sources
- US EPA — Mold and moisture guidance — the 30–50% range and the 10 sq ft remediation threshold
- ASHRAE Standard 55 — Thermal environmental conditions for human occupancy — indoor comfort and humidity limits
- US DOE 10 CFR 430 — Dehumidifier test procedure — the 2019 move to 65 °F rating conditions
- NOAA / NWS 1991–2020 Climate Normals, via the city climate tables on Wikipedia
- US Department of Energy — Building America climate zone definitions
- EPA — Indoor Air Quality: moisture control and mold
- DOE 10 CFR 430 — dehumidifier test procedure (2019 method)