Wind Rose Explained

Wind Roses are helpful tools which display wind speed and direction at a specified season and location.

What is it measuring?

The Wind Rose displays three types of information: 

  • The direction from which wind is blowing 
  • The speed at which wind is blowing
  • How often wind blows from a particular direction at a particular speed

Wind direction (where wind is blowing from, not towards) is displayed in a compass configuration.

The shade of each ‘spoke’ of the wind rose indicates a range of speeds at which wind blows, based on the legend displayed at the bottom. For instance, winds blowing from a particular direction may typically be low-speed, but might occasionally become much stronger.

Finally, the radiating rings – and the accompanying numbers displayed with each ring – indicate how often wind blows from that direction at various speeds. This is shown as a percentage. 

How to Read a Wind Rose

During the Spring season at Toronto Pearson Airport, wind blows from due East for a total of 4.6% of the season. These winds blow at:

0-10 km/h for ~0.5% of the season

10-20 km/h for ~1.2% of the season

20-30 km/h for ~1.8% of the season

30-40 km/h for ~0.8% of the season

40+ km/h for ~0.3% of the season.

From the southerly direction (see below), winds typically blow from the southeast. These SE winds are low-speed, typically blowing at 10-20 km/h, and do not exceed 30 km/h. Winds from the southwest – on the other hand – are far less frequent, but much more intense; when wind blows from the SW direction, they are typically above 20 km/h and sometimes exceed 40 km/h. Therefore, despite blowing less frequently than from the SE, these SW winds are considerably more impactful.