Montana design temperatures
Outdoor heating and cooling design conditions for 12 Montana weather stations. Choose the station nearest to you in distance and elevation, and check whether your building department specifies its own values.
| Station | Elevation | 99.6 % heating | 99 % heating | 1 % cooling / MCWB | 0.4 % cooling / MCWB | Use it |
|---|---|---|---|---|---|---|
| Billings/LoganWMO 726770 · 1973–1996 | 3,570 ft | −13 °F | −7 °F | 91 / 62 °F | 94 / 63 °F | Load calculator |
| Butte/MooneyWMO 726785 · 1973–1996 | 5,545 ft | −25 °F | −16 °F | 84 / 56 °F | 87 / 57 °F | Load calculator |
| Cut BankWMO 727796 · 1973–1996 | 3,855 ft | −20 °F | −15 °F | 84 / 59 °F | 88 / 60 °F | Load calculator |
| GlasgowWMO 727680 · 1973–1996 | 2,297 ft | −23 °F | −17 °F | 90 / 63 °F | 94 / 64 °F | Load calculator |
| Great FallsWMO 727750 · 1973–1996 | 3,658 ft | −18 °F | −12 °F | 88 / 60 °F | 92 / 61 °F | Load calculator |
| HavreWMO 727770 · 1973–1996 | 2,599 ft | −24 °F | −18 °F | 90 / 62 °F | 94 / 63 °F | Load calculator |
| HelenaWMO 727720 · 1973–1996 | 3,898 ft | −17 °F | −10 °F | 88 / 60 °F | 91 / 61 °F | Load calculator |
| Kalispell/GlacierWMO 727790 · 1973–1996 | 2,973 ft | −12 °F | −3 °F | 86 / 62 °F | 89 / 63 °F | Load calculator |
| LewistownWMO 726776 · 1973–1996 | 4,167 ft | −18 °F | −11 °F | 86 / 60 °F | 89 / 60 °F | Load calculator |
| Malmstrom AFBWMO 727755 · 1967–1996 | 3,527 ft | −18 °F | −11 °F | 89 / 61 °F | 92 / 61 °F | Load calculator |
| Miles CityWMO 742300 · 1973–1996 | 2,628 ft | −19 °F | −13 °F | 94 / 65 °F | 97 / 66 °F | Load calculator |
| Missoula/Bell FieldWMO 727730 · 1973–1996 | 3,189 ft | −9 °F | 0 °F | 89 / 62 °F | 92 / 63 °F | Load calculator |
Using these values
- Heat-loss calculations for homes commonly use the 99 % heating value, and cooling loads the 1 % dry bulb with its mean coincident wet bulb (MCWB). The 99.6 % and 0.4 % values are more conservative.
- “Load calculator” opens the heating and cooling load calculator with that station’s 99 % and 1 % temperatures and its design moisture difference (outdoor air at the 1 % condition versus 75 °F, 50 % RH indoors, at the station’s elevation).
- Source: U.S. Air Force Combat Climatology Center and NOAA National Climatic Data Center, Engineering Weather Data (1999; public domain). Each station’s period of record is shown under its name; they end by 1996, and the climate has warmed since, so check local requirements before relying on a value for a permit.