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Pre-Bloom in a Dry Corridor

Willamette Valley — May 18, 2026

Where We Stand

Through May 18, the valley has accumulated 256 GDD (base 50F) across 48 days since April 1. This week added 35 of those degree days, with a high of 76F and a low of 38F — a wide diurnal swing that reflects classic mid-May conditions in this corridor. Precipitation came in at 0.44 inches. Bud break was recorded April 4, and the vines are now in pre-bloom. That progression from bud break to pre-bloom in 48 days is the number worth holding onto as the next phase approaches.

The Week Ahead

The seven-day forecast shows highs ranging from 68F to 77F with zero precipitation across all seven days. That sustained dry window, combined with temperatures consistently in the upper 60s to mid-70s, will push GDD accumulation forward at a meaningful rate. The models show no interruption to that accumulation through the forecast period. For vines already at pre-bloom, the trajectory into bloom is now largely a question of how long this warm, dry pattern holds.

Season Context

An April 4 bud break followed by a dry, warm run into late May sets a particular kind of tone. The 256 GDD figure through mid-May reflects a season that has moved with reasonable consistency — neither a slow start requiring recovery nor an aggressive early push that creates compression later. The absence of precipitation in the forecast extends what has already been a relatively dry stretch in the critical window before bloom. Historically, Willamette Valley bloom timing and set quality are shaped significantly by the weather in the ten to fourteen days surrounding flowering. That window is approaching. The pattern going into it deserves attention.

Season GDD Tracker

073147220294 Apr 01Apr 09Apr 17Apr 25May 03May 11 256 GDD 2026 Cumulative GDD (Base 50F)
Cumulative Growing Degree Days (base 50F, cap 86F) from April 1. Willamette Valley, Oregon.

7-Day Outlook

Mon
May 18
68°
44°
Tue
May 19
69°
47°
Wed
May 20
69°
45°
Thu
May 21
76°
46°
Fri
May 22
75°
46°
Sat
May 23
77°
46°
Sun
May 24
76°
42°
This week at a glance: High 76F · Low 38F · 0.44" precip · 35 GDD accumulated · Season total: 256 GDD
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