Tree pollen season in Cornwall, CT ran from roughly mid-April through late May 2026, with a peak window of three weeks (Apr 21–May 10) that consistently registered High or higher on both Pollen.com and AccuWeather. The season tail lingered longer than the climatological calendar predicted — moderate-level readings persisted through May 25.
This report combines every morning reading from the cornwall-tree-pollen-alert cron job, which checked three live sources daily at 5 AM ET and sent an alert when conditions were noteworthy. Only about 18 of the 38 days in the monitoring window triggered alerts — the rest were quiet days where pollen and weather didn't warrant a message.
| Date | Pollen.com | AccuWeather | Notes |
|---|---|---|---|
| Apr 19 | 6.1 · Med | Moderate | |
| Apr 20 | 6.1 · Med | Moderate | Gusts 24 mph |
| Apr 21 | 10.4 · High | High | Season kicks into gear |
| Apr 22 | 6.8 · Med | High | Sources disagreed |
| Apr 24 | 11.1 · High | High | Highest reading of April |
| Apr 25 | 10.2 · High | High | |
| Apr 29 | 10.8 · High | High | 5-day: 10.8→10.8→10.1→6.0→10.1 |
| Date | Pollen.com | AccuWeather | Notes |
|---|---|---|---|
| May 3 | 11.0 · High | Extreme | 5-day: 11.0→10.7→9.8→10.7→11.3 |
| May 6 | 7.7 · Med-High | High | Wind gusts 31 mph |
| May 8 | Low→High climb | High | Gusty 21 mph |
| May 9 | 6.1 · Med | High | Down from 10.4 yesterday |
| May 10 | 9.9 · High | Moderate | Warmup 56→70°F, gusts 20 mph |
| May 14 | 0.5 · Low | Very High | Wild source disagreement |
| May 18 | 10.3 · High | — | 5-day rising to 11.7 |
| May 21 | 8.9 · Med-High | Extreme | First possible easing sign |
| May 22 | 9.4 · Med-High | High | Still elevated late May |
The static pollen-calendar-zone6a.json — a climatological norm for Zone 6a NW Connecticut — predicted the season shape well through early May, but late May ran 1–2 tiers higher than expected.
| Week | Calendar | Actual Peak | Gap |
|---|---|---|---|
| Apr 20 | high | 10.4–11.1 High | ✅ On track |
| Apr 27 | very_high | 10.8 High | ✅ |
| May 4 | very_high | 11.0 High | ✅ |
| May 11 | high | 9.9–10.3 High | ✅ |
| May 18 | moderate | 8.9–10.3 Med-High | ⚠️ +1 tier |
| May 25 | moderate | 9.4 Med-High | ⚠️ +1 tier |
Key takeaway: In a warm spring, plan for the "moderate" tail weeks (May 18–31) to actually hit Med-High. The calendar is a solid baseline, but it underpredicted the late-season persistence by about a week.
Source Behavior
- AccuWeather runs hot. It consistently rated 1–2 tiers above Pollen.com across the entire season. Its "Extreme" tier (above "Very High") appeared multiple times when Pollen.com showed merely High or Med-High.
- Pollen.com "season completed" bug. From mid-April onward, Pollen.com's page displayed a boilerplate "the pollen season in the area has completed" message — even while showing a High numerical index of 10.4+. This is a stale fallback and should be disregarded.
- When they disagree, the truth is usually in between but closer to AccuWeather for symptom prediction.
Season Shape
- Peak window: Apr 21–May 10 — three solid weeks of High+ readings on both sources.
- Season tail: May 11–25 — readings stayed Med-High to High, ~1–2 weeks longer than the calendar predicted.
- Grass overlap: Grass pollen started registering Low in early May and ramped to Moderate/High by late May, extending the overall allergy season even as tree pollen began to fade.
- Rain ≠ relief. Rain temporarily suppressed airborne pollen, but dry/warm rebounds hit hard within 24–48 hours. A rainy weekend followed by a warm Monday was the most common "trap" pattern.
- Apr 27–May 11: Plan for peak season. This window is reliable year over year. If you're going to travel to escape tree pollen, this is the window to miss.
- Late May lingering: Budget for the tail to overrun the calendar by about a week. The "moderate" weeks (May 18–31) are likely to be Med-High or High in a warm spring.
- AccuWeather's "Extreme" is real. When you see it, trust it as a symptom signal — it appeared on days that matched the worst symptom reports.
- Grass season overlap: By mid-May, grass pollen compounds the misery even as trees start to ease. Don't declare victory on tree pollen alone.
Every morning at 5:00 AM EDT, a cron job queried three live sources:
- Pollen.com — JSON API for ZIP 06753 (current index + 5-day forecast)
- AccuWeather — West Cornwall / Cornwall Bridge tree pollen allergen forecast
- NWS — Point forecast for Cornwall, CT for weather context (wind, rain, temperature)
The job sent a concise alert to Telegram only when tree pollen was High+ or when weather would aggravate moderate levels. Readings were NOT logged persistently — they were recovered retroactively from session archives. A proper logging script has been designed for 2027.
Pollen.com index scale: 0–2.4 Low · 2.5–4.8 Low-Med · 4.9–7.2 Med · 7.3–9.6 Med-High · 9.7–12 High