Mold inspection and indoor air help in Billings, MT
We do not keep an office in Billings. Every job starts with a free call. For large and complex properties in the Billings 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 Billings climate does to a house
Measured at NOAA's Billings weather station.
- At the NOAA Billings station, mornings average 63 percent relative humidity across the year, and afternoons 45 percent.
- The dampest mornings come in March, averaging 66 percent. Afternoons are driest in August, at 30 percent.
- A normal year brings 13.66 inches of precipitation over about 97 days, with the most in May (2.18 inches).
- No month averages 80 percent morning humidity, which is why mold here almost always traces back to a water event rather than damp air.
| Month | Morning RH | Afternoon RH | Precip. (in) | Days with precip. | Mean temp (°F) |
|---|---|---|---|---|---|
| January | 64% | 58% | 0.48 | 8 | 27.1 |
| February | 64% | 53% | 0.48 | 7 | 30.4 |
| March | 66% | 48% | 1.06 | 9 | 37.7 |
| April | 65% | 43% | 1.66 | 10 | 46.2 |
| May | 66% | 43% | 2.18 | 12 | 55.6 |
| June | 66% | 40% | 2.12 | 11 | 64.7 |
| July | 58% | 31% | 1.32 | 7 | 72.8 |
| August | 56% | 30% | 0.75 | 6 | 71.5 |
| September | 60% | 37% | 1.30 | 7 | 60.3 |
| October | 61% | 45% | 1.18 | 7 | 48.2 |
| November | 63% | 54% | 0.63 | 6 | 35.8 |
| December | 63% | 57% | 0.50 | 7 | 26.5 |
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 Billings 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 45 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 97 days a year bring measurable precipitation, most of it in May.
Evaporative coolers
Swamp coolers cool by adding water to the air. Poorly maintained ones add humidity and their own microbial growth to the house. 30 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 13.66 inches of rain, so irrigation water often outweighs rainfall at the foundation.
Common questions from Billings
Large, custom or multi-property situations: see Keystone.
Mold or air problem in Billings?
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.