Newcastle, WA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Newcastle, a city in King County, Washington.
Overnight
52°F
Mostly Cloudy
Mostly cloudy, with a low around 52. Southeast wind around 2 mph.
7-day forecast for Newcastle
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 52°F | Mostly Cloudy | 2 mph SE | 0% |
| Saturday | 72°F | Partly Sunny | 2 mph WSW | 0% |
| Saturday Night | 53°F | Mostly Clear | 2 mph NNE | 0% |
| Sunday | 72°F | Mostly Sunny | 3 mph N | 0% |
| Sunday Night | 52°F | Mostly Clear | 3 mph NNE | 0% |
| Monday | 71°F | Mostly Sunny | 3 mph N | 0% |
| Monday Night | 53°F | Partly Cloudy | 3 mph NNE | 1% |
| Tuesday | 68°F | Partly Sunny | 2 mph NNW | 1% |
| Tuesday Night | 52°F | Mostly Cloudy | 2 mph ESE | 7% |
| Wednesday | 68°F | Partly Sunny then Slight Chance Light Rain | 3 mph WSW | 16% |
| Wednesday Night | 52°F | Slight Chance Light Rain then Mostly Cloudy | 2 mph N | 16% |
| Thursday | 64°F | Mostly Cloudy then Slight Chance Light Rain | 5 mph NNE | 21% |
| Thursday Night | 51°F | Slight Chance Light Rain | 5 mph NNE | 21% |
| Friday | 63°F | Slight Chance Light Rain | 5 mph N | 16% |
Forecast source: National Weather Service (api.weather.gov) for Newcastle (47.531, -122.166). Updated through the day.
Growing snapshot for Newcastle
Last spring frost
Mar 13
First fall frost
Nov 16
Growing season
248 days
Hardiness zone
8b
More local growing data for Newcastle: nearby ZIP 98006 weather · frost dates · planting calendar · Washington frost dates
Nearby towns & communities
Algona
Ames Lake
Auburn
Baring
Beaux Arts Village
Bellevue
Black Diamond
Bothell
Boulevard Park
Bryn Mawr-Skyway
Burien
Carnation
Clyde Hill
Cottage Lake
Covington
Des Moines
Duvall
East Renton Highlands
Fairwood
Fall City
Federal Way
Greenwater
High Bridge
Hobart
Hunts Point
Index
Issaquah
Kenmore
Kent
Kirkland
Climate data from the nearest NOAA station, Renton Muni Ap, Wa (5.1 mi from Newcastle). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.