An extremely rare display of lightning occurred over Peru's capital city Lima on Monday morning.

While lightning is common in Australia, it almost never happens along the arid Pacific west coast of Peru.

This made Monday morning's lightning display over Lima a bit of a surprise, with locals caught out by what may have been a once-in-a-generation thunderstorm.

Image: Enhanced infrared (top) and visible (bottom) satellite images, with lightning strike data overlay, showing Monday morning's thunderstorm over Lima.

Lima doesn't usually get directly hit by thunderstorms because the atmosphere above the west coast of Peru is almost always too stable.

Thunderstorms need three ingredients to develop: atmospheric instability, sufficient moisture and a trigger that causes air to rise.

The air near Lima is kept relatively cool throughout the year by a channel of cold water called the Humboldt Current, which flows up the west coast of South America. Because this cold low-level air is denser than the warmer air that sits above it, the uplift that's required for thunderstorm development can't happen.

But on Monday, a unique set of conditions caused early-morning lightning directly above Lima.

Relámpagos y lluvia en Lima (porque ahora si puedo decir que es lluvia). Eso es nuevo âš¡ ☔ pic.twitter.com/RvUFdOaH9v

— Oh Boy ∞ (@Ataque_Verbal) May 24, 2021

According to the National Service of Meteorology and Hydrology of Peru, the storms were caused by an offshore upper-level area of low pressure called an Isolated Depression at High Levels (also called a Depresión Aislada en Niveles Altos or DANA).

This broad area of cold upper-level air caused a spike in atmospheric instability along the coast of Peru on Monday. This instability allowed storms to develop off the coast before moving towards the southeast and marching directly over Lima.

truenos en Lima. Se aproximan las elecciones. Voten bien. ⚡️⚡️⚡️ #Lima #truenos #relampagos #random pic.twitter.com/CTRiZ9E6ee

— Claudia Miyasato 🦄 (@claudiamiyasato) May 24, 2021

The National Service of Meteorology and Hydrology of Peru said that Lima's lightning was as "unusual meteorological phenomenon".

"This anomalous event for Lima had not been registered since 1960, when another electrical storm developed that generated lightning over the capital city," they said in a press release.

Peru's Ministry of Environment has announced that they are investing in radar and lightning detection equipment that will form an Early Warning System to better monitor and forecast weather events like this one in the future.