Ukko possessed a weapon, often a hammer called Ukonvasara, sometimes also an axe or a sword, by which he struck lightning.
Thunderstorms were sometimes interpreted as result of Ukko copulating with his wife Akka. He also was believed to cause thunderstorms by driving his chariot through the skies.
A viper with a serrated line on its back was considered a symbol of thunder.
There is evidence that the rowan tree was held sacred to Ukko. Rauni, a vaguely defined being has been hypothesised to be cognate to Germanic words for the rowan tree.
The ladybird was also considered sacred to Ukko and called ukonlehmä