Mold inspection and indoor air help in Yakima, WA
We do not keep an office in Yakima. Every job starts with a free call. For large and complex properties in the Yakima 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 Yakima climate does to a house
Measured at NOAA's Yakima weather station.
- At the NOAA Yakima station, mornings average 72 percent relative humidity across the year, and afternoons 44 percent.
- The dampest mornings come in December, averaging 84 percent. Afternoons are driest in July, at 25 percent.
- A normal year brings 8.25 inches of precipitation over about 70 days, with the most in December (1.53 inches).
- In 3 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 | 83% | 72% | 1.14 | 9 | 31.0 |
| February | 79% | 57% | 0.78 | 7 | 36.1 |
| March | 72% | 42% | 0.62 | 7 | 43.2 |
| April | 66% | 34% | 0.55 | 5 | 49.1 |
| May | 64% | 31% | 0.58 | 5 | 57.1 |
| June | 63% | 30% | 0.62 | 5 | 63.9 |
| July | 61% | 25% | 0.22 | 2 | 70.6 |
| August | 63% | 27% | 0.26 | 3 | 69.3 |
| September | 69% | 32% | 0.36 | 3 | 60.8 |
| October | 75% | 44% | 0.54 | 5 | 49.0 |
| November | 81% | 63% | 1.05 | 8 | 37.3 |
| December | 84% | 76% | 1.53 | 10 | 28.5 |
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 27, 2026.
Where moisture hides in Yakima homes
Plumbing leaks nobody sees
In a dry climate, mold is almost always a water event, not humidity. Slow leaks under sinks, behind dishwashers and in slab plumbing can run for months before anyone notices. Afternoons here average just 44 percent humidity, so damp air is rarely the cause.
Short, violent storm seasons
When the rain does come it comes hard. Roofs, parapets and flat-roof drains that sit dry most of the year fail all at once. Only about 70 days a year bring measurable precipitation, most of it in December.
Evaporative coolers
Swamp coolers cool by adding water to the air. Poorly maintained ones add humidity and their own microbial growth to the house. 36 days a year reach 90°F or more, which is when coolers run hardest.
Pools, spas and irrigation
Water features and landscape irrigation next to the foundation keep one side of a house damp in an otherwise dry place. A normal year brings only 8.25 inches of rain, so irrigation water often outweighs rainfall at the foundation.
Common questions from Yakima
Large, custom or multi-property situations: see Keystone.
Mold or air problem in Yakima?
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.