Growing degree days in Seattle, WA
Season to date · base 50°F · since January 1
1,355GDD
Active growth
The lawn is growing hard. This is the productive window for nitrogen, and where PGR sprays pay off most because the grass is putting on clippings fastest.
Through 2026-08-01 · Open-Meteo archive
How the heat has built this year
Cumulative growing degree days since January 1. Each day adds the average of that day’s high and low, minus a 50°F base, with nothing added on days that stay below it.
PGR reapplication tracking
Plant growth regulator timing uses a Celsius-scale accumulation, not the seasonal Fahrenheit one. This page tracks a 10°C base, which is the Bermuda (warm-season) figure. Trinexapac-ethyl is typically re-sprayed near 200 GDD on cool-season turf and roughly 216 to 230 on warm-season turf, measured from your last application rather than from January. Always follow the product label.
Track GDD from your own spray date →Soil temperature right now in Seattle, WA
GDD is a trend indicator. Soil temperature is the signal that actually decides pre-emergent and seeding timing, and it is 66.6°F here at 2 inches.
Full soil report for 98101 →Get this number every morning
This page recalculates when you load it. The app accumulates GDD for Seattle, WA daily and tells you when your PGR window opens. Free on iPhone and Android.