WorkWindow

Lawn Seeding Weather in Beaverton, OR: 10-Day Windows & Best Months

Beaverton is one of the rare places where lawn seeding weather never fully closes: every month averages 8 or more workable days by NOAA 1991–2020 normals. March leads the calendar with 31 workable days: average high 58°F, low 42°F, rain on 63% of days. The strip above runs Beaverton's live forecast; the table below ranks all 12 months.

GOOD — clears every rule MARGINAL — exactly one soft miss NO — a hard fail, or two soft

The rules this check uses

Every seeding verdict above is this table against Beaverton's hours. Cool-season numbers, no humidity rows (damp is good here), and a washout threshold where the cure window would be.

Typical label thresholds for lawn seeding — the ruleset behind every Beaverton verdict above.
CheckThresholdWhy it matters
Air temperature 50–85°F (low-temp formulas from 55°F) Checked across the working day, 8 a.m.–6 p.m., against Beaverton's hourly forecast — not just the daily high.
Overnight low ≥32°F during the first 48 h (≥40°F preferred) The engine reads every overnight hour in the cure window, not just Beaverton's forecast low.
Dry before no soaking (≥1.0") in the prior 24 h Seeding into mud makes ruts and washes seed into low spots.
Dry after <0.5" rain for 24 h after Light rain after seeding helps. A 0.5"+ downpour washes seed out.
Wind ≤15 mph (broadcast seed drifts up to 25 mph) Wind wrecks application first (drift, lap marks) and carries debris into wet work second.

Always follow your product label — formulas vary. These rows are the industry-typical range; the can in your Beaverton garage is the contract.

Best months for lawn seeding in Beaverton

Workable days in Beaverton, OR: days meeting the temperature rules, discounted by NOAA rain odds — a 1991–2020 estimate, not a forecast.
MonthAvg highAvg lowRain odds/dayWorkable days 
January 50°F 40°F 64% 12
February 54°F 40°F 62% 29
March 58°F 42°F 63% 31
April 63°F 45°F 56% 30
May 70°F 50°F 44% 31
June 73°F 53°F 33% 30
July 81°F 56°F 14% 31
August 82°F 57°F 13% 31
September 76°F 52°F 32% 30
October 65°F 47°F 53% 31
November 55°F 43°F 63% 30
December 49°F 40°F 61% 2

There is no off-season to plan around in Beaverton — the planning question is week-to-week, not month-to-month. The leanest stretch is December (2 workable days, average high 49°F); the richest is March with 31. For the statewide picture, the Oregon page compares peak months city by city.

Beaverton has a real wet/dry rhythm: January brings rain on 64% of days versus 13% in August. When the calendar gives you a August-side window, the dry-before and dry-after rules nearly take care of themselves.

Opposite-weather pairing: the showers that help a seedbed void the cure window over at deck staining in Beaverton.

Numbers above come from NOAA's 1991–2020 normals for Nature Park-Beaverton, Or Us, 2.9 km from the city center — close enough that neighborhood microclimates (shade lines, river valleys, urban heat) matter more than station distance. See how these day counts are scored.

Beaverton by the numbers

Prep checklist

  1. Calendar first: Beaverton hits the 55–80°F band mostly in March and May — 31 workable days in March alone.
  2. Scalp and bag, then dethatch — germination needs seed-to-soil contact, not seed-on-thatch.
  3. Broadcast with a broadcast spreader at the bag rate; over 15 mph, the light fractions drift off-target.
  4. Feed roots, not weeds: starter fertilizer now, weed-and-feed only after 2–3 mows.
  5. Rake seed in an eighth to a quarter inch and roll or walk it for contact.
  6. Topdress slopes with peat moss topdressing — January is Beaverton's washout month (10% odds of a half-inch day).
  7. Keep the top half-inch damp until sprout: an oscillating sprinkler bridges Beaverton's gaps between March rains (63% of days).
  8. First mow at 3 inches, blades high, and stay off the new stand between cuts.

Gear that saves a window

FTC note: the gear below is unlinked until the affiliate program is switched on. See the affiliate disclosure.

FAQ

When is it too cold to plant grass seed?

Cool-season seed wants 50°F+ highs (ideally 55–80°F) and nights over 40°F to keep germination moving; a freeze within 48 hours is the hard stop. Beaverton's soil-warmth proxy — average highs — clears 55°F around January, which is where the spring window opens.

Will rain wash away grass seed?

Ordinary showers help; downpours carve. The engine fails a seeding day when 0.5"+ is forecast within 24 hours and flags 0.25–0.5". In Beaverton, January carries the real washout risk (10% odds of a half-inch day); August almost none.

Is spring or fall better for seeding in Beaverton?

March and may top Beaverton's table. The classic fall-wins rule holds where summers are brutal; here the numbers above are the honest tiebreaker.

How much rain is too much right after seeding?

The engine draws it at 0.5" in the 24 hours after seeding (hard fail) and 0.25–0.5" (flag). Slopes fail first — seed migrates downhill and sprouts in stripes. In Beaverton, that check matters most in January (10% half-inch-day odds). Seed 2–3 days ahead of a front, or wait behind it.

How long does grass seed need water after planting?

Daily light watering (sometimes twice) until sprout, then taper to deep-and-infrequent. Rain counts toward the schedule: Beaverton averages measurable rain on 63% of March days. What kills seedbeds is cycling soaked-to-bone-dry in one afternoon.

What months are best for seeding in OR?

For Beaverton: March, May and July, with March at 31 workable days in the 55–80°F germination band. Cool-season math — warm-season grasses (bermuda, zoysia) invert it toward early summer. The OR state page compares every listed city.

Other projects in Beaverton

Lawn Seeding nearby

Guides

Climatology: NOAA 1991–2020 normals via NATURE PARK-BEAVERTON, OR US (2.9 km from Beaverton center, elevation 185 ft); live outlook by Open-Meteo.