Record-setting dry spell leaves Southwestern Ontario farmers waiting (and waiting) for rain

Jun 07, 2023

The London region has just completed the driest local May ever, Environment Canada officials say – with only 4.1 millimetres of rainfall recorded, a drop in the bucket compared to April’s 92.1 mm.

“What a difference a month can make,” said Environment Canada meteorologist Gerald Cheng. “That’s a record.”

Cheng offered up another figure that made the lack of rain even more stark: An average May gets 89.8 mm of precipitation, or roughly 22 times as much as was recorded last month.

May 2023’s dry conditions tromp on 1954’s previous local record low for the month, 13.8 mm of rain. But Cheng says there were six days during which the national weather agency’s official instruments at London International Airport failed to report properly and data potentially was missing.

With little rain in the forecast, drought-like conditions will continue.

Lack of movement in the atmosphere – called a Rex block – has been preventing weather systems from moving into southern Ontario, Cheng said. A Rex block occurs when a low-pressure system is hanging over the United States and produces sunny conditions and warm weather to the north.

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Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.