“Cloud seeding destroyed their homes and livelihoods,” one Facebook post about community anger in Spain claims.

A different post is captioned “scum pilots flooded Spain”.

Some posts blame cloud seeding programs in nearby Morocco for a "climate conspiracy" that caused the weather events in Spain.

Cloud seeding has previously been linked to major flood events, including the Dubai floods earlier this year and the 2022 Queensland floods.

It's a form of weather manipulation that involves introducing particles, such as silver iodide, into clouds via aircraft or ground-based generators.

In theory, the substance provides particles for water droplets to converge around. When the droplets join the particle, they become heavy enough to fall to the ground as rain.

It is used in various countries with limited natural rainfall, including in parts of Australia, to varying degrees of success.

However, experts told AAP FactCheck cloud seeding cannot produce the level of rainfall witnessed in Spain that left more than 200 people dead.

The country was hit by intense rains across October 29 and 30, with some areas receiving a year’s worth of rain in a matter of hours.

Roelof Burger, an atmospheric science expert from North-West University in South Africa, said cloud seeding could not have created, or intensified, the weather event.

“The energy involved and scale of the system is much larger than what current seeding technology is capable of modifying,” Professor Burger said.

Spanish meteorologist Roberto Granda agreed, telling AAP FactCheck there is no possibility that the Spanish floods were linked to cloud seeding.

“Cloud seeding plans have been under research for decades in many countries and, until now, no conclusive results have ever been obtained that demonstrate an increase in rainfall,” he said.

“That is, they are of no use at the moment according to scientific evidence.”

Rather, he said the storm was the result of what was called a DANA (depresion aislada en niveles altos, or isolated high-altitude depression) weather system. This happens when cold and warm air meet in the upper and middle layers of the atmosphere, creating powerful rain clouds.

Michael Manton, an emeritus professor at Monash’s School of Earth Atmosphere and Environment, previously told AAP FactCheck cloud seeding can be effective when the natural processes to form rain is “not operating to full capacity”.

He said cloud seeding could not cause huge weather systems and will instead just “squeeze a little (but valuable) extra rain from those clouds”.

Some posts have linked the High-frequency Active Auroral Research Program (HAARP) to the flooding.

HAARP is a research project at the University of Alaska Fairbanks that studies the earth’s ionosphere.

AAP FactCheck has debunked several false claims linking HAARP to weather events, such as Hurricane Milton and the northern lights.

Experts have previously told AAP FactCheck that HAARP cannot affect weather.

That's because the program interacts with ionised particles – electrons – in the ionosphere, well above the range where weather formations occur.

“Radio waves in the frequency ranges that HAARP transmits are not absorbed in either the troposphere or the stratosphere – the two levels of the atmosphere that produce earth’s weather,” a University of Alaska Fairbanks spokesperson told AAP FactCheck.

“Since there is no interaction, there is no way to control the weather.”