Expected to start in ~5 days (~30 Apr 2027). Likely start range (80% of past weather years): 17 Apr 2027 – 8 May 2027. Expected flowering length: ~20 days (measured in Sweden).
Backtested against 35 years of local observations at this city (leave-one-year-out); the model beat simple climatology.
Typical error if the weather were known (model backtest, MAE): 2.96 days; 89% of years within ±5 days.
Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±6.17 days. Months ahead, the weather is unknown, so expect about this much.
Observations used: 35 years at this city (1991–2025).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Forsythia in Hanover validated
Season over. Next expected start ~19 Mar 2028. Likely start range (80% of past weather years): 7 Mar 2028 – 8 Apr 2028. Expected flowering length: ~14 days (assumed, not measured).
Backtested against 35 years of local observations at this city (leave-one-year-out); the model beat simple climatology.
Typical error if the weather were known (model backtest, MAE): 4.71 days; 69% of years within ±5 days.
Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±11.23 days. Months ahead, the weather is unknown, so expect about this much.
Observations used: 35 years at this city (1991–2025).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Wood anemone in Hanover validated
Expected in bloom now (started ~25 Mar, ends ~30 Apr). Likely start range (80% of past weather years): 19 Mar 2027 – 3 Apr 2027. Expected flowering length: ~36 days (measured in Sweden).
Backtested against 35 years of local observations at this city (leave-one-year-out); the model beat simple climatology.
Typical error if the weather were known (model backtest, MAE): 4.56 days; 69% of years within ±5 days.
Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±5.8 days. Months ahead, the weather is unknown, so expect about this much.
Observations used: 35 years at this city (1991–2025).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Sweet cherry blossom in Hanover validated
Expected in bloom now (started ~14 Apr, ends ~27 Apr). Likely start range (80% of past weather years): 5 Apr 2027 – 21 Apr 2027. Expected flowering length: ~13 days.
Backtested against 24 years of local observations at this city (leave-one-year-out); the model beat simple climatology.
Typical error if the weather were known (model backtest, MAE): 3.75 days; 79% of years within ±5 days.
Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±5.03 days. Months ahead, the weather is unknown, so expect about this much.
Observations used: 24 years at this city (1991–2023).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Horse chestnut in Hanover validated
Expected to start in ~5 days (~30 Apr 2027). Likely start range (80% of past weather years): 20 Apr 2027 – 9 May 2027. Expected flowering length: ~14 days (assumed, not measured).
Backtested against 35 years of local observations at this city (leave-one-year-out); the model beat simple climatology.
Typical error if the weather were known (model backtest, MAE): 2.53 days; 89% of years within ±5 days.
Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±6.49 days. Months ahead, the weather is unknown, so expect about this much.
Observations used: 35 years at this city (1991–2025).
Observed first-bloom date by year (city median of observers) vs. model expectation:
“Start” = first flowers open (BBCH 60), not the peak. Peak is usually later; we have no open peak data. Individual gardens differ by ±4–8 days from the city median. See How it works and Sources.