Whether your home is damaged by an autumn hurricane, winter snowstorm, spring flood or summer drought, the tax laws can take the sting out of the situation through a federal income tax deduction.

Damage to your house and yard from an unexpected source can be deducted as a casualty loss, says Prentice-Hall, publishers of tax guidelines.

"Casualty" includes damage from a disaster such as a tornado, fire or earthquake.

Other deductible "casualties" -- not limited to natural disasters -- include several that would surprise the average homeowner. They are "unusual" and "unavoidable."

This latter category includes bursting of water heaters, cave-ins due to adjacent excavations, long and unusual droughts, explosions, freezing and bursting of water pipes, ice and sleet, sonic booms of jet planes and vandalism. It also includes lightning, sinking of land caused by subterranean disturbances, smog, termites (if damage occurs in a relatively short time), unusually high waves and wind.

What losses qualify? Physical losses to all property you own are deductible -- including losses in your house, garage, trees, furniture, rugs and drapes. But not all financial losses from casualties qualify -- for example, the cost of moving and renting temporary quarters is not deductible.

How much is deductible? The deduction, according to Prentice-Hall, is the lesser of 1) actual loss in value -- that is, the value of your home before the loss less the value after -- or 2) the tax basis (cost plus improvements) of your property. The lesser figure then is reduced by $100 plus any reimbursement received, such as insurance.

Your house, garage, shrubs and trees are treated as a unit in figuring your loss. If a storm damages trees in your yard, you can take a deduction only if there is a decrease in the value of your property as a whole. That stately elm may have had a special esthetic value -- but what counts for tax purposes is the drop in value of the entire property. If household furnishings also are damaged, your deduction for them is figured separately.

How about clean-up expenses? Such expenses after a storm, for example, are deductible.

Proof must be complete and objective. Your best proof is "before and after" photos. If you were hit by a recent storm and haven't done so already, take snapshots of the damage you suffered immediately. These pictures are just about the best proof of the extent of the damage -- especially when coupled with shots of the "before."

If you haven't been doing it previously, get set taxwise for possible future casualties by taking periodic pictures of your house and grounds. That way, the "before" is always up to date.

If the damage is extensive, you may want to get the written report of an independent appraiser. The appraiser's report will help you nail your deduction, and the fee he charges is deductible.

When to deduct? The loss generally may be deducted only on the return for the year in which the casualty occurs.

There's one big exception: If you suffered a loss in a government-designated disaster area, you either may file an amended return for the prior year and deduct the loss against the prior year's income or deduct the loss on the current year's return. There may be special problems when insurance enters the picture. You may suffer a casualty in one year, but are not reimbursed until the following year.

Prentice-Hall suggests that you deduct the estimated amount not covered by insurance. When you settle with the insurance company, adjust the difference on your next year's tax return.

If your casualty losses exceed the year's salary income, you have a net operating loss. This not only relieves you of any tax for that year, but it can be carried back to recover taxes paid in three previous years.

If still not used up, the loss can be carried over as a deduction for the next seven years. Because the actual computation of a net operating loss can get complicated, Prentice-Hall suggests consulting an experienced tax adviser.