Lightning can produce gamma rays and antimatter

According to recent reports the very strong fields produced by the lightning accelerate electrons close to the speed of light colliding with atoms to create gamma photons. According to Phys.org:

Terrestrial gamma flashes were discovered about two decades ago. When lightning strikes, electrons are accelerated to very high energies and crashing into air molecules, causing an explosion of gamma radiation, the so-called terrestrial gamma flashes.

More recetly it was discovered that some of these gamma rays can have enough energy to produced antimatter. See this report:

...researchers from Japan describe how gamma rays from lightning react with the air to produce radioisotopes and even positrons—the antimatter equivalent of electrons.