Uppsala Sweden
Expected first-bloom dates for spring 2027, based on a degree-day temperature model and years of observations. 16 Oct 2026 status shown.
| Flower | Status today | Expected start | Likely range | Reliability | Model error (backtest) |
|---|---|---|---|---|---|
| Lilac | Season over | ~24 May 2027 | 17 May – 28 May | validated | 3 d |
| Forsythia | Season over | ~24 Apr 2027 | 12 Apr – 4 May | approximate | n/a |
| Wood anemone | Season over | ~14 Apr 2027 | 5 Apr – 26 Apr | approximate | 6.44 d |
| Sweet cherry blossom | Season over | ~10 May 2027 | 4 May – 15 May | approximate | 3 d |
| Horse chestnut | Season over | ~24 May 2027 | 19 May – 29 May | approximate | n/a |
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Lilac in Uppsala validated
Season over. Next expected start ~24 May 2027. Likely start range (80% of past weather years): 17 May 2027 – 28 May 2027. Expected flowering length: ~20 days.
Backtested against 12 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 days; 92% of years within ±5 days.
- Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±4.09 days. Months ahead, the weather is unknown, so expect about this much.
- Observations used: 12 years at this city (2008–2024).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Forsythia in Uppsala approximate
Season over. Next expected start ~24 Apr 2027. Likely start range (80% of past weather years): 12 Apr 2027 – 4 May 2027. Expected flowering length: ~14 days (assumed, not measured).
No (or far too few) usable open observations in this country for this flower; the model parameters were fitted on German data and transferred and are unchecked here. In our lilac test, transferring the German model to Sweden was off by about 4 days on average (bias about +3.8 days). Model parameters: transferred from Germany.
- Typical error if the weather were known (model backtest, MAE): not measured.
- Typical error of a long-range estimate like this one (spread of past years at this city, MAE): not measured. Months ahead, the weather is unknown, so expect about this much.
- Observations used: 0 years at this city.
No local observation series to show for this flower here.
Wood anemone in Uppsala approximate
Season over. Next expected start ~14 Apr 2027. Likely start range (80% of past weather years): 5 Apr 2027 – 26 Apr 2027. Expected flowering length: ~36 days.
Not called validated: backtest error 6.44 days is above our 5-day bar; the model did not beat simple climatology here.
- Typical error if the weather were known (model backtest, MAE): 6.44 days; 59% of years within ±5 days.
- Typical error of a long-range estimate like this one (spread of past years at this city, MAE): ±4.76 days. Months ahead, the weather is unknown, so expect about this much.
- Observations used: 17 years at this city (2008–2024).
Observed first-bloom date by year (city median of observers) vs. model expectation:
Sweet cherry blossom in Uppsala approximate
Season over. Next expected start ~10 May 2027. Likely start range (80% of past weather years): 4 May 2027 – 15 May 2027. Expected flowering length: ~16 days.
Not called validated: only 1 years of local observations for this city.
- Typical error if the weather were known (model backtest, MAE): 3 days; 100% of years within ±5 days.
- Typical error of a long-range estimate like this one (spread of past years at this city, MAE): not measured. Months ahead, the weather is unknown, so expect about this much.
- Observations used: 1 years at this city (2013–2013).
No local observation series to show for this flower here.
Horse chestnut in Uppsala approximate
Season over. Next expected start ~24 May 2027. Likely start range (80% of past weather years): 19 May 2027 – 29 May 2027. Expected flowering length: ~14 days (assumed, not measured).
No (or far too few) usable open observations in this country for this flower; the model parameters were fitted on German data and transferred and are unchecked here. In our lilac test, transferring the German model to Sweden was off by about 4 days on average (bias about +3.8 days). Model parameters: transferred from Germany.
- Typical error if the weather were known (model backtest, MAE): not measured.
- Typical error of a long-range estimate like this one (spread of past years at this city, MAE): not measured. Months ahead, the weather is unknown, so expect about this much.
- Observations used: 1 years at this city (2013–2013).
No local observation series to show for this flower here.
“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.