Newcastle, WY Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Newcastle, a city in Weston County, Wyoming.
This Afternoon
80°F
Mostly Sunny
Mostly sunny, with a high near 80. West wind around 3 mph.
7-day forecast for Newcastle
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 80°F | Mostly Sunny | 3 mph W | 6% |
| Tonight | 56°F | Chance Showers And Thunderstorms | 3 mph E | 73% |
| Saturday | 68°F | Showers And Thunderstorms Likely | 1 to 6 mph SE | 69% |
| Saturday Night | 52°F | Showers And Thunderstorms Likely | 5 mph SE | 74% |
| Sunday | 61°F | Showers And Thunderstorms | 5 mph SE | 95% |
| Sunday Night | 49°F | Showers And Thunderstorms | 3 mph SE | 83% |
| Monday | 64°F | Chance Rain Showers | 1 to 8 mph SE | 31% |
| Monday Night | 50°F | Mostly Clear | 8 to 12 mph SE | 2% |
| Tuesday | 70°F | Mostly Sunny | 8 to 12 mph SE | 7% |
| Tuesday Night | 54°F | Slight Chance Rain Showers then Mostly Clear | 7 to 12 mph SE | 17% |
| Wednesday | 75°F | Mostly Sunny then Slight Chance Showers And Thunderstorms | 6 mph SE | 20% |
| Wednesday Night | 53°F | Mostly Clear | 3 mph E | 11% |
| Thursday | 76°F | Sunny | 2 to 6 mph SE | 5% |
| Thursday Night | 54°F | Partly Cloudy | 7 mph SE | 6% |
Forecast source: National Weather Service (api.weather.gov) for Newcastle (43.850, -104.196). Updated through the day.
Growing snapshot for Newcastle
Last spring frost
May 20
First fall frost
Sep 23
Growing season
123 days
Hardiness zone
4b
More local growing data for Newcastle: nearby ZIP 82723 weather · frost dates · planting calendar · Wyoming frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Upton, Wy (11.4 mi from Newcastle). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.