Boston's very cool June....

Fourth coldest June since 1885....

Since the sun virtually disappeared on June 5, hidden behind an impenetrable pall of cement-colored clouds, Robert Skilling has tracked each overcast moment, anticipation building with each gray afternoon.

Peering out at the gloom from his perch at the Blue Hill Meteorological Observatory and Science Center, Skilling does not dwell on the canceled Little League games or postponed beach days.

Rather, he focused yesterday on the primitive, softball-sized glass sphere on the observatory’s roof, a device that has burned lines on paper since 1885 to record nearly every burst of sunshine strong enough to cast a faint shadow. This month, the sun has been obscured by clouds more than in any other June in Skilling’s 50-plus years of meteorology. With a little more than a week remaining, it is flirting with the all-time local record set in June 1903, when only 25 percent of the sun’s rays penetrated the clouds to reach the Blue Hills.

“We are down to 32 percent for the month,’’ Skilling, 71, said with the apprehensive joy of a baseball fan in the ninth inning of a no-hitter. “That’s a solid second place, for now.’’

Skilling has hard meteorological evidence of something that virtually every resident of the Boston region knows in their core: The sun has taken a hiatus, leaving the area with the dreariest June in memory.

Skilling looks at weather the way Alex Rodriguez looks in the mirror: He can’t get enough. He revels in the data, celebrating the anomalous and basking in the extreme. That could be a frighteningly strong wind, a blizzard of snow, a torrent of rain. Now it’s a depressing absence of sunshine that keeps him so upbeat.

He knows about this deficiency because of his glass sphere, known technically as a pyroheliometer, that has been on the roof of the observatory since it opened in 1885. (A few years ago the observatory replaced the original pyroheliometer when it was stolen by a college student who scaled the tower during a night of revelry. The original was recovered and kept as a model to show guests.)

The technology is as simple as burning a leaf with a magnifying glass. The glass sphere focuses the light and creates heat. The burn is recorded on green, rain-resilient cardboard that is curved like a banana to follow the trajectory of the sun. Each day someone changes the card and measures the burn marks.

Holding a stack of the used cards from June in his hand, Skilling traced the region’s sunless misery.

“Three days in a row,’’ Skilling said, flipping through unburned cards from June 9, 10, and 11. “This is what was making people feel bad.’’

His other weather data bear it out: The dreariness has been compounded by a genuine coolness, with an average temperature of 59.8 degrees so far this month, making this the fourth coldest June since the observatory opened in 1885. Rain is also a half-inch above average, giving New England a summer chill more common in Ireland.