Newcastle, WA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Newcastle, a city in King County, Washington.
Today
57°F
Partly Sunny
Partly sunny. High near 57, with temperatures falling to around 52 in the afternoon. North northwest wind around 3 mph.
7-day forecast for Newcastle
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 57°F | Partly Sunny | 3 mph NNW | 3% |
| Tonight | 42°F | Mostly Clear | 2 mph ESE | 3% |
| Wednesday | 57°F | Mostly Sunny then Slight Chance Light Rain | 3 mph S | 15% |
| Wednesday Night | 49°F | Light Rain | 2 to 13 mph S | 93% |
| Thursday | 57°F | Slight Chance Light Rain then Partly Sunny | 3 to 9 mph SSW | 23% |
| Thursday Night | 48°F | Light Rain | 3 to 8 mph SSE | 78% |
| Friday | 56°F | Light Rain | 3 to 8 mph SSE | 78% |
| Friday Night | 48°F | Chance Light Rain | 3 mph SSE | 47% |
| Saturday | 61°F | Chance Light Rain | 3 mph SSE | 29% |
| Saturday Night | 51°F | Light Rain Likely | 2 to 15 mph S | 73% |
| Sunday | 56°F | Light Rain Likely | 3 to 15 mph SSW | 73% |
| Sunday Night | 46°F | Slight Chance Light Rain | 3 mph SE | 19% |
| Monday | 56°F | Chance Light Rain | 3 mph SE | 51% |
| Monday Night | 48°F | Light Rain Likely | 2 to 9 mph SSE | 69% |
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 Nov 3, 2026.