In order to prevent we must first understand; we must identify the source of these precipitationous men. How is it possible that this multitude of fully grown, rough, tough, strong and mean men first came to be falling from the sky? There are a few theories - research into each is paramount.

Preparation relies on the cause; therefore several defensive conditions have been devised in order to adequately equip the populace with the appropriate HPD equipment. See HPDCON section below.

Possible causes:

Mass Religious Suicide
A huge suicidal cult hires a fleet of planes and fills them with thousands of devotees. They do not take parachutes.
__Prevention__ – A religious watchdog is set up to infiltrate emerging cultist movements and report any inclinations of mass suicide. At the same time an international law is passed by the UN banning the appropriation of aircraft by religious groups.
__Preparation__ – HPDCON 3

Hurricane over men’s prison
During a mass scrub-down in the yard of a large prison for men, an extremely strong localised twister lifts all of the inmates up into the air and deposits them over a nearby town.
__Prevention__ – Provide prisons with state of the art barometers and weather predicting utilities in order to schedule unnecessary external mass scrub-downs during least-risk times.
__Preparation__ – HPDCON 3

US military death-row trebuchet programme
Due to lack of resources, the US military begin to use death row inmates as missiles in large trans-Atlantic trebuchets capable of hurtling a grown man from Texas to the Middle East within a degree of accuracy of 120 miles. Either these trebuchets are used gratuitously by the US resulting in a constant barrage of humans across the Middle East and Europe, or they lose control of them to other powers who turn them on their creators.
__Prevention__ – UN sanctions to be enforced against nations using human projectiles.
__Preparation__ – HPDCON 3 - If left unchecked, the death-row trebuchet programme could result in a chronically sustained, though moderate-density, human rainfall barrage due to the huge number of death row inmates in the US, and the inevitable increase in death sentences for minor offences as the government attempt to provide further ammunition.
Coastal cities across Western Europe should erect enormous nets to catch the inmates, where they will be rounded up and escorted under guard to freighters bound for Australia.

Freak hospital-plane cloud-insemination accident
A plane transporting human semen and eggs accidentally dumps its cargo mid-flight in the centre of an enormous storm cloud, within which the eggs are fertilised and gestate. When fully grown the humans fall to Earth.
__Prevention__ – This theory has been widely confronted with scepticism due to the lack of heat and nutrition in a cloud. However, if it were possible, these humans would not pose as much of a threat, being made up mostly of water. Moreover, simple precautions can be taken in the transportation of ovum and spermotazoon, illud est, separately. Like the Royal family.
__Preparation__ – HPDCON 1

Parallel Universe
A theory first expounded by Prof. Jerry Gorshwicz (of no fixed abode) illustrates how the Universe is in constant friction with its parallel equivalents. His theory, generally aired when given food, or change for a cup of tea, is that these, “Worlds in opposition can cause God damn miraculous and otherwise unexplainable events garble garble!” He goes on to say, “Trust in me you wretched heathens, the other place shall open its unholy mouth and garble forth a monstrous saturate of men upon this Earth. And lo, the ladies shall rip off their roofs and stay in bed, yet they shall perish under the destructive force of man, you piddling, garbling swines you!”
__Prevention__ – Gorshwicz believes that atonement will be enough. Also, if we give him three ham sandwiches a day, and enough cider to fill a cup, he will personally protect our planet from the trans-dimensional rift.
__Preparation__ – HPDCON 3 – Unknown quantity, likelihood and frequency of human precipitation. Standard safeguards should be implemented in areas infamous for spectral and/or supernatural phenomenon. Coastal cities near the Bermuda triangle, local villages of Loch Ness in Scotland, and Transylvania should all be considered for the scheme.

Care Bear bestiality
The male genitalia of a Care Bear is said to be barbed, like a dog’s or a spider-monkey’s. It is possible that female Care Bears have been abducting male humans to procreate in comfort. Indeed, some millennia ago this cross-species inter-breeding may have been the genetic spark for the species’ comparative intelligence, moral code and social awareness. Perhaps sometime in the near future a rebel faction of despondent male Care Bears rises up and expels the human men from their place in the clouds, throwing them to a horrible and messy death thousands of miles below.
__Prevention__ – Mass surveillance to be installed in children’s bedrooms to recover intel on Care Bear movements and intentions. Fleet of Harrier Jump Jets on stand-by in various locations around the globe, ready to destroy Care Bear Land in a barrage of AAM, possibly nuclear-tipped warheads.
__Preparation__ – HPDCON 4

Mother Nature
As a single woman, Mother Nature might enjoy one too many glasses of wine and get knocked up by some randy angels.
__Prevention__ – It would be unwise to prevent Mother Nature the ability to create life (possibly by saturating the planet with progestogen), however, the opposing solution - ie catching and castrating angels - poses its own problems. For one, their physical existence is questionable. If indeed they do exist their powers of elusion are so adept it is unlikely we would be able to find one. Therefore, if Mother Nature and the angels are responsible for an impending storm of human precipitation there is likely no prevention possible.
__Preparation__ – HPDCON 5 - Total worldwide anarchy. A global catastrophe.

Human Precipitation Defence Condition

HPDCON 1
Large, metal umbrellas should be provided for those venturing out into a rainstorm, which should be enough to disperse any watery men that fall on someone.

HPDCON 2
Personal surface-air radar to detect incoming human projectiles made available for purchase. General reinforcement of roofs, bus shelters, and cars etc.

HPDCON 3
Areas of escalated risk are fitted with either nets to catch humans or angled shoots and slides to feed them into nearby incinerators. Nets will be manned with armed guards for the incarcerationally challenged, or to place innocent newcomers to our planet in quarantine to be processed and duly released into society.

HPDCON 4
There is no HPDCON 4.

HPDCON 5
Fully integrated system of survival against a potentially endless storm of human precipitation. This includes:
1.) Concave spires to be erected over every building, remotely adjusted to point towards the incoming humans. These are connected to a system of shoots and slides feeding incinerators in order to destroy as much of the flesh as possible.
2.) There will also be an emergency curfew law and warning system to ensure all civilians are out of danger as quickly as possible.
3.) Food delivery to bomb shelters can be made in emergencies via tanks.
4.) Lock your doors and close your mind. You'll probably only have a 2 minute warning.

________________________

Further research and deliberation will be required to devise a CADCON, in order to prepare us for when it rains cats and dogs.

(Care Bear, Parrallel Universe and Mother Nature theories proposed by my colleague and esteemed apprentice 'baker [sugar pants])