What a wonderful time: summer heat is past; great harvest holidays approach. Time to contemplate one of the greatest and most unusual wines in the world: Madeira, an ideal wine to enjoy at the warm, fuzzy end of a feast or while snuggling in a favorite blanket as the first chills of winter whisper outside.

Madeira is part of Portugal, but it is an island some 625 miles southwest of the mainland, almost due west of Casablanca, Morocco.

Madeira wine is made like no other, and it has properties like no other. Because its making involves heat it is incredibly durable—the world’s longest-living wine. Some Madeira bottles do not reach maturity until a century or more of aging. Even simplest stuff is five to 10 years old.

Production involves the estufa system, a process that duplicates long, hot sea voyages that finished original Madeiras. Simplest methods involve artificially heating the wine to 130 degrees for at least three months. Second method heats the wine to 100 degrees for six months to a year. Most expensive method warms the wine by natural sunlight for 20 to 100 years. Then it ages in a cask for decades.

At the high end, Madeira makers count on their great grandchildren-plus to judge their work. Bottles exist for sale from 1715, recent sales included bottles from 1790 and 1808. The simplest stuff is five years old; 10-plus years is common; 50-year-old bottles are not rare.

If you have never tasted Madeira, you owe yourself a taste. It is not for everyone, but it can become a go-to, special delight. It is fortified wine, usually flirting with 19 percent alcohol. At its best, striking acidity balances tasty sweetness. Madeira comes in four distinct styles (and an impostor):

• Malmsey: start here. Sweetest, most approachable style; smooth, delicious, mahogany brown color; acidity balances sweetness. World-class malmsey hits its peak after a century of aging, but 10-year-old infants can be excellent.

• Bual: slightly less sweet than malmsey, medium rich, raisiny, reddish-brown color.

• Verdelho: tangy acidity, smoky, medium dry, orange-amber color.

• Sercial: driest, most mouth-puckering. Almond-like aromas, pale gold color, most acidic, austere.

• Rainwater: not a true style and not a good test for Madeira—too often a label put on inexpensive, overly-sweet bottlings that do not have the cutting acidity that balances classic Madeira.

Producers: Leacock, Blandy’s, Sandeman, Rare Wine Company are ones you are most likely to find. You probably will have to take whatever you can get at your wine store, but it is a delicious, special wine to try, and several experts predict it is the Next Big Thing. Ride the wave. Try madeira.

Last round: I don’t have a wine drinking problem. I have a problem when I’m not drinking wine.