ROSEVILLE - If you want to find the Roseville weather station, just follow the well-worn path across the lawn from David Wallwork's front door.

Wallwork, 77, has tread the route around 30,000 times since 1972, and could probably walk it with his eyes closed. A few paces from his garden, a white wooden box on posts called a Stevenson screen holds two thermometers. The plastic rain gauge sticks out of the ground just past that.

Twice daily, the retired engineer steps outside his stone farmhouse off Fischer-Hallman Road and records the temperature and precipitation. He does his readings at the same time every day, blizzards or thunderstorms be damned.

Wallwork's observations are sent to Environment Canada, where it's added to the national climate data archive. From there, it's used by everyone from farmers and insurance adjusters to municipal budget planners and engineers.

The work is all volunteer, although this year Environment Canada sent Wallwork a flashlight so he could read the instruments in the dark.

"It's only weird people like us who want to do this," he said with a chuckle. "In the winter time, it's grim. You get settled in here, it's dark and then you've got to go outside and read the blooming gauge out there. It does become a pain in the neck."

Environment Canada meteorologist David Phillips, the unofficial dean of weather in Canada, says it's getting harder and harder to find people willing to do the work that Wallwork does.

There's about 120 volunteer weather observers left in Ontario today, roughly two-thirds fewer than in 1990, meaning there are more gaps in the data around our weather patterns. So much of our weather information now comes from automated weather stations, like the one at the Region of Waterloo International Airport.

Having someone like Wallwork doing the same observations over such a long time is increasingly rare - and a blessing to meteorologists, Phillips said.

"Over those years, you get a really good trend analysis. You're dealing with the same site, same observer, same methods. That's like gold," he said. "It's invaluable when you're trying to concern yourself with climate change."

But even Wallwork, who likes that his readings help meteorologists more accurately detect and evaluate local severe weather events, says he doesn't know how much longer he'll be able to keep it up.

His three adult daughters have all long since left the farm and it's a lot of work for him and his wife Judith to maintain their sprawling rural property.

"We'll try to hold on as long as we can. But at some point, we'll have to bite the bullet and move into town," he said. "It would be nice if it will continue. But whether someone will actually do it, I don't know."

Wallwork used to record the data by hand in big blue ledgers, and then mail his findings once a month to Ottawa. Telephone reporting eventually replaced the mail, and now everything is reported online.

When he went on vacation, he would get someone to make the recordings for him.

Running the Roseville weather station remains a remarkably manual, low-tech operation in today's digital world. Since there's only four numbers involved (the day's high, low and current temperature, plus precipitation), Wallwork doesn't take a notepad. He just keeps the readings in his head until he walks back inside.

His tools are two thermometers (one alcohol-based, the other using mercury), a round rain gauge that measures precipitation, a wooden snow stick and a pine "snow board" - replaced a few years ago after the dog chewed off the handle.

Wallwork started 42 years ago when he heard CBC weatherman Percy Saltzman say Environment Canada was looking for volunteer weather watchers, and he signed up. He likes that his work gives localized weather for a region where thunderstorms can mean vast differences in rainfall just a few kilometres apart.

The hottest day he ever recorded was 36.5 C, on Aug. 8, 2001. The rainiest? That was 92 millimetres on July 29, 1991, more than 3.6 inches. And who can forget Jan. 23, 1976, when the thermometer plunged to a numbing -31.7 C.

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Over four decades, he's noticed some trends in his daily recordings, too. Among them are observations that back up what climatologists tell us about our warming planet: our winters are getting milder, with less snow, and our summers are hotter.

But Wallwork could have told you that even without his daily recordings.

"We used to have so much snow here. Now we can't get enough to even build a snow fort," he said. "Maybe 40 years is a short-term trend, but that trend is there. I think we have to recognize it, and start doing something about it."