Mold inspection and indoor air help in Houston, TX
We do not keep an office in Houston. Every job starts with a free call. For large and complex properties in the Houston area we travel to you; for smaller jobs we tell you exactly what to ask for and point you to a local inspector we are comfortable recommending.
What the Houston climate does to a house
Measured at NOAA's Houston weather station.
- At the NOAA Houston station, mornings average 89 percent relative humidity across the year, and afternoons 59 percent.
- The dampest mornings come in July, averaging 93 percent. Afternoons are driest in August, at 56 percent.
- A normal year brings 52.69 inches of precipitation over about 103 days, with the most in June (5.55 inches).
- In 12 of 12 months the average morning humidity is 80 percent or higher.
- Even in the afternoon, average humidity stays above 60 percent in 3 of 12 months. Indoors, 60 percent is the line where mold starts to find it easy.
| Month | Morning RH | Afternoon RH | Precip. (in) | Days with precip. | Mean temp (°F) |
|---|---|---|---|---|---|
| January | 85% | 62% | 4.22 | 10 | 53.3 |
| February | 86% | 61% | 3.18 | 8 | 56.8 |
| March | 87% | 59% | 3.03 | 9 | 62.5 |
| April | 89% | 57% | 3.52 | 7 | 69.0 |
| May | 91% | 58% | 4.54 | 8 | 76.1 |
| June | 92% | 59% | 5.55 | 9 | 81.6 |
| July | 93% | 57% | 4.71 | 9 | 83.0 |
| August | 93% | 56% | 4.35 | 9 | 83.3 |
| September | 92% | 58% | 5.26 | 9 | 79.0 |
| October | 90% | 56% | 5.46 | 8 | 71.4 |
| November | 89% | 59% | 4.78 | 8 | 62.5 |
| December | 87% | 62% | 4.09 | 9 | 54.9 |
Source: NOAA National Centers for Environmental Information, Comparative Climatic Data: average relative humidity (period of record through 2018), normal precipitation, mean temperature and cooling degree days (1981 to 2010 normals), and mean days with 0.01 inch or more of precipitation, 90 degrees or more, and 32 degrees or less. Last updated September 24, 2026.
Where moisture hides in Houston homes
Air conditioning that runs most of the year
Every hour the AC runs, it pulls water out of the air into a drain pan and a condensate line. A clogged line or a slimy pan is one of the most common sources of hidden water damage and musty vents in warm climates. Here a normal year runs to 2,940 cooling degree days.
Ducts and air handlers in hot attics
Cold ducts running through a hot, humid attic sweat. That water soaks insulation and drywall below, often with no visible leak. 104 days a year reach 90°F or more.
Humid outdoor air getting inside
Leaky ducts, unsealed crawlspaces and bathroom fans that pull air from outside all bring damp air into cooled rooms, where it condenses on the coldest surfaces. Summer mornings here average 93 percent humidity.
Storms and wind-driven rain
Heavy rain events push water through windows, flashing and roof penetrations. The damage often shows up weeks later as a stain or a smell. The wettest month here averages 5.55 inches.
Common questions from Houston
- Musty Smell When AC Turns On
- Mold on AC Evaporator Coil
- Ductwork Smells Moldy
- AC Drain Pan Overflow or Slime
Large, custom or multi-property situations: see Keystone.
Mold or air problem in Houston?
Start with a free 15 minute call. We will tell you what you need, whether that is a local inspector, a virtual consultation or an on-site investigation.