Loading lots of data. Please wait.

Showing forecast for: Change Location

Click a year and then drag the slider to view actual results below and historical predictions to the left.
Drag the marker on the map to change the location of the forecast.

The Five Predicted Events

Leaftime predicts 5 popular events in the life cycle of a leaf.


This brief video gives a short explanation of how the predictions are made. It also highlights some of the benefits that come from understanding more about the life cyles of leaves.


Leaf phenology is the seasonal timing of leaf development and is of general public interest for amateur naturalists who are interested in when leaves emerge in spring, and change colors in fall. The timing of these natural biological phenomena is driven by abiotic drivers, primarily the seasonal cycle of temperature.

How it Works

The life cycle events of a leaf depend significantly on the cumulative temperatures of the year. Each unit is called a growing-degree day. It is computed by subtracting a base temperature from the average temperature of the day. Each life cycle event of a leaf usually occurs once a certain number of Growing-Degree Days have passed. For example a bud break event may occur for a certain species at 30 growing-degree days.

The steps to make the prediction are as follows:

  1. Satelite images of past years are analyzed to determine when the events occured. This analysis involves measuring differences in color hues and infrared values. The day of the event is then converted to a growing-degree day value by calculating all of the temperatures as described previously.

  2. Now that the growing degree day value of the events is known, the current year-to-date growing-degree day value is calculated.

  3. By combining the year-to-date growing-degree day value with forecasted growing-degree day values, we are able to make a prediction of when a leaf event will occur.

Geocoding information provided by GeoNames.org