By Robb M. Stewart

OTTAWA--Canada's trade surplus ballooned to its widest in four years as exports hit a record high on the back of a strong lift in shipments of metals and minerals and the continued benefit of higher crude-oil prices.

The country recorded a May merchandise-trade surplus of 4.24 billion Canadian dollars, the equivalent of about US$2.99 billion--the largest since May 2022, Statistics Canada said Tuesday.

Canada has now racked up trade surpluses three months running as exports have rebounded following a weak start to the year. May's surfeit was wider than the C$2.68 billion expected by economists, and it follows April's upwardly revised C$3.41 billion surplus.

Exports overall climbed 0.9% to their highest level on record for the latest month, buoyed by a rise in goods sent to the U.S., while imports dipped 0.2% between April and May. The result was that Canada's longstanding goods-trade surplus with its biggest market by far expanded to C$11.63 billion, the largest since the record high in January 2025, while the trade deficit with all other countries widened modestly.

Increased prices for oil and other commodities as the Middle East conflict dragged on played a big role in driving the value of exports. In volume terms, exports were essentially unchanged while imports were up 0.4% month over month.

Canadian trade surpluses can come and go quickly with swings in oil prices, and this reading is likely the high-water mark for now, said Robert Kavcic, senior economist at Bank of Montreal Capital Markets. "Still, net exports look to add firmly to growth in the second quarter, another data point that suggests the Canadian economy has snapped out of its two-quarter funk," he said.

The slight lift in import volumes also points to improving domestic demand, a positive for an economy that has struggled since last year's shift in U.S. trade policy and tariffs.

Exports increased broadly in May, and surged 26% on a year earlier. Shipments of energy products slipped 2% for the month after a jump in April, though they were up a little more than 70% year over year thanks to the jump in oil prices with the Iran war.

The largest rise in exports was in metal ores and nonmetallic minerals. Shipments of sulfur from Canada were up sharply as global supplies were constricted by the war and the squeeze on goods moving through the Strait of Hormuz. Canadian exports of gold also increased during the month, and exports of unwrought aluminum and aluminum alloys rose to their highest value in four years with deliveries to the Netherlands, Italy and Greece.

Excluding energy products, overall exports for the month were up 2% from April.

On the import side, inbound goods pulled back from the record-high level in April, largely due to a decline in metals and minerals and a drop in gold purchases. Imports of consumer goods rose in May, driven by batteries and battery chargers from China, and imports of pharmaceutical and medicinal products rose, mainly coming in from Germany, the U.S. and Spain.

An earlier flash estimate by Statistics Canada suggests gross domestic product ticked up 0.1% in May from the month prior, which puts the economy on track for growth of more than 2% in annualized terms for the second quarter. This, while modest, would mark a recovery after the economy contracted a slight 0.1% annualized in the first quarter and 1% in the final quarter of 2025.

With oil prices having fallen in recent weeks, the value of exports and the trade surplus may have seen a near-term peak in May, economists say. And uncertainty has risen again after the U.S. last week declined to extend the U.S.-Mexico-Canada trade pact, known as USMCA or CUSMA, in its current form. The pact remains in effect but the U.S. refusal to renew means trade officials from the three countries will have to meet every year for a decade to continually review the deal.

"Even though CUSMA wasn't extended last week, the fact that the trade deal remains in place and most exports maintain an exemption from U.S. tariffs should help maintain higher export volumes relative to a year ago, alongside ongoing [Canadian] efforts to grow trade with other countries, which today's data suggest are paying dividends in some sectors," said Andrew Grantham, senior economist at CIBC Capital Markets.

Write to Robb M. Stewart at robb.stewart@wsj.com