Gardening Weather

Does a Cold, Rainy June Mean a Cold, Rainy Summer?

A common belief suggests that the month of June determines the weather for the rest of the summer. Is there any truth to that?

By Larry Hodgson

Question: My grandfather, a farmer, always said, “When June is cold and wet, the rest of the season will be unpleasant.” It seems to me he’s right. That most cold, wet Junes led to cold, wet summers. This year, June seems to be one of the coldest and wettest ever. What are your thoughts on this?

David

Answer: “When June is cold and wet, the rest of the season will be unpleasant” is actually quite a common saying. Something that might have appeared in an old Farmer’s Almanac, perhaps. At any rate, I’ve heard exactly that quote many times.

But, first, it’s not easy to extrapolate on anything when it comes to weather. To start with, your remark “This year, June seems to be one of the coldest and wettest ever” may apply in some areas. And certainly in the eastern part of North America, it has indeed been exceptionally cool, gray and wet in June. But not everywhere. Other areas are already suffering from heat and drought!

That said, though, on a local level, a cold, wet, gray June often does lead to a cooler summer. At least taking strictly temperate Northern Hemisphere climates into consideration.

Temperature Lag

Table showing warm weather following one month behind the seasonal change.
Temperatures, shown as a pink band on this illustration, tend to follow hours of sunlight, but with a delay of one month.. Ill.: nvent2HelpAll, Wikimedia Commons

This is due to something called temperature lag or seasonal lag. It just takes time for the sun’s energy to overcome cold conditions. That’s why the autumnal equinox (around September 22) is considerably warmer than the vernal equinox (around March 20) in most regions. This is despite the fact that both days have almost equal amounts of daylight and darkness.

In the Northern Hemisphere, the summer equinox (June 20 or 21) is the day when the Hemisphere receives the most solar energy. So, you’d think it would also correspond to the hottest temperatures. But because of the lag, that generally occurs about 1 month later. And in most temperate climates, August, in spite of its shorter days, is a much hotter month than June.

So, if June is exceptionally cool, it will take extra time to warm up the atmosphere. And for summer heat to set in. As a result, often the entire summer ends up being cooler than average.

Expect Exceptions!

Of course, we’re talking about the weather here, and it is so famously changeable. So, clearly you can have a cold June, but then see summer heat arrive rapidly and take over. And also, even if a summer is considered a cold one overall, that doesn’t mean it won’t have its hot days.

Let’s say the chances of a cool summer after a cool June increase. If you look at the pattern over many areas, more than two out of every three summers following a cold June will be cool ones.

As for Rain

In many temperate climates, a cool June is often a gray June, with lots of cloud cover and plenty of rain. I’m not sure what the theory behind why gray, rainy weather persists into the summer is, but it does seem to be true . . . on average. (Yes, there are always exceptions!)

Table comparing wet and dry summers for the city of Montreal.

In a recent weather report for Montreal by the Weather Network, for example, a table showed a wet June led to a wet summer 69% of the time, while a dry one led to a dry summer 61% of the time. So there seems to be a rain lag as well.

Just Garden!

There isn’t much the home gardener can do about the weather, though, is there? Just put out extra slug bait (slugs love cool, moist summers), put on your rain hat and rubber boots and plan on harvesting lots of lettuce, bok choy and Swiss chard and not so many early tomatoes!

3 comments on “Does a Cold, Rainy June Mean a Cold, Rainy Summer?

  1. After the searing heat and smoke of last summer a cooler damper summer will be welcome.

  2. Our cool and wet weather ended a long time ago. (chaparral climate)

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