Every year, more and more Americans retire abroad. About 615,000 Americans received their Social Security checks outside the U.S. last month, up 57 percent since 2000. That doesn’t count thousands of additional Americans who live abroad full- or part-time but continue receiving checks at U.S. banks. 

Those checks just became a lot more valuable, too. After a decade in the doldrums, the dollar has gotten significantly stronger. The U.S. Dollar Index, which measures the value of a dollar against a basket of international currencies, is up 25 percent since July, boosting the buying power of expatriate retirees, from Buenos Aires to Paris.  

Jim Horn, a retired professor who lives in Cuernavaca, Mexico, figures his daily expenses are down 11 percent—and that’s before a recent further drop in the Mexican peso. Horn says he already had a comfortable income from Social Security and a pension priced in dollars. “So I am living quite well,” he says. His only regret: He put the proceeds of a condo sale in a Mexican bank, rather than his U.S. account. The Mexican peso is down 17 percent since last year’s high.

Not all these retirees are benefiting equally. The low cost of living in Panama helped almost triple the number of American retirees there since 2001. But the strong dollar hasn’t made life any cheaper because the Panamanian balboa is pegged to the dollar. In neighboring Costa Rica, also a popular retirement spot for Americans, the Costa Rican colon is up slightly this year — though it is down 6.4 percent from the beginning of 2014.

But other countries just got a lot cheaper:

The most noticeable benefit of a strong dollar may be to Americans in higher-cost places. London still isn't a bargain: The pound is down 5.5 percent year-to-date and 12 percent since the beginning of last year. The currencies in both Japan and Canada are down 15 percent since last July. Euro area countries, on the other hand, are a heck of a deal: The euro is down 24 percent against the dollar over the past 12 months.  

In practical terms, this means that retirees can spend less of their dollar-denominated savings, which means the whole nest egg should last longer. Retirees who tap 10 percent less of their portfolio each year can stretch money for five additional years with the same level of risk, according to the Vanguard Retirement Nest Egg Calculator. 

That assumes that retirees don't deploy their newfound wealth in wild spending, although renters could consider buying real estate overseas. Regardless of the strength of the dollar, financial advisers recommend that expats put at least six months of living expenses into local currency and diversify their portfolios by making sure a hefty portion of stocks and bonds are invested outside the U.S. If most of your expenses are in euros, it makes sense that most of your assets be euro- denominated, too.

Mary Duncan moved to Paris in 2001, after retiring early from her job as a San Diego State University professor. She says the weaker euro is letting American expats eat out more often, travel more, buy more books, and “feel a little more secure financially.” That said, she doesn’t expect the windfall to last forever. “Those of us who have lived in Paris for more than 10 years know this is cyclical,” she says.