Altona, CO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Altona, a community in Boulder County, Colorado.
This Afternoon
80°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Mostly cloudy. High near 80, with temperatures falling to around 69 in the afternoon. South wind around 5 mph. Chance of precipitation is 50%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Altona
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 80°F | Chance Showers And Thunderstorms | 5 mph S | 48% |
| Tonight | 54°F | Chance Showers And Thunderstorms then Partly Cloudy | 5 mph WSW | 28% |
| Saturday | 73°F | Slight Chance Rain Showers then Chance Showers And Thunderstorms | 1 to 6 mph SW | 68% |
| Saturday Night | 49°F | Chance Showers And Thunderstorms then Slight Chance Showers And Thunderstorms | 2 mph WNW | 43% |
| Sunday | 69°F | Chance Showers And Thunderstorms | 2 mph NE | 41% |
| Sunday Night | 49°F | Chance Rain Showers then Partly Cloudy | 2 mph N | 30% |
| Monday | 70°F | Sunny | 0 to 5 mph ENE | 5% |
| Monday Night | 50°F | Mostly Clear | 2 mph N | 7% |
| Tuesday | 74°F | Mostly Sunny then Chance Showers And Thunderstorms | 2 mph ENE | 26% |
| Tuesday Night | 52°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 0 to 3 mph W | 20% |
| Wednesday | 75°F | Partly Sunny then Chance Showers And Thunderstorms | 0 to 3 mph ENE | 26% |
| Wednesday Night | 52°F | Slight Chance Rain Showers then Mostly Cloudy | 2 mph SW | 18% |
| Thursday | 75°F | Mostly Sunny then Slight Chance Showers And Thunderstorms | 1 to 5 mph NE | 19% |
| Thursday Night | 53°F | Chance Rain Showers then Mostly Cloudy | 2 mph WSW | 25% |
Forecast source: National Weather Service (api.weather.gov) for Altona (40.122, -105.296). Updated through the day.
Growing snapshot for Altona
Last spring frost
May 6
First fall frost
Oct 5
Growing season
151 days
Hardiness zone
6a
More local growing data for Altona: nearby ZIP 80304 weather · frost dates · planting calendar · Colorado frost dates
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Climate data from the nearest NOAA station, Boulder, Co (3.8 mi from Altona). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 18, 2026.