If homicides have decreased in Boston over the past few months because of the weather, that would hardly account for the fatal shooting of Soheil Turner.

The 15-year-old student was shot on May 7, a rainy morning, outside a convenience store on Dudley Street. According to investigators, the killer, who was wearing dark sunglasses, was equipped with a .380 semi-automatic handgun and an umbrella.

Since the day Turner was shot, Boston has had an abnormally high number of cloudy days and – by comparison with last year – a decrease in the rate of homicides. Some observers say the recent drop in homicides and shootings can be explained in part by the weather. But others say the reasons could include everything from efforts by law enforcement and medical personnel to anti-violence programs and the neighborhood walks by community volunteers.

From the beginning of this year through July 19, there have been 27 homicides in Boston, down 25 percent from the figure from the same date last year. Homicides are also down in some other large cities around the country. The weather has been cited for the decrease in New York City, but the Washington Post reports homicides are also down in cities with different weather patterns, including D.C. and Los Angeles.

In Boston, the decrease in homicides has been very noticeable in areas that have usually experienced the most violence. In Area B (Roxbury, Mattapan and part of Dorchester), there have been 5 homicides since Turner was killed, but only one since June 14: the stabbing death of a 49-year-old man on July 27. In Area C (Dorchester and South Boston), over the same period of almost seven weeks, there has been one homicide – a 74-year-old man allegedly stabbed by a 64-year-old woman.

About a week after Turner was shot, a 3-year old boy and a 70-year-old woman were struck by shots fired into a store on Bowdoin Street by a 16-year-old suspect. The shootings were non-fatal, but the next day, Mayor Menino and Police Commissioner Ed Davis were on Bowdoin Street to announce they would increase patrols and visibility in “hot spot” areas.

Even by last December, there were plans for a violence prevention strategy with a new way of deploying street workers funded by the Boston Foundation. Instead of only city street workers who finished their shift at 8 p.m., the “Street Safe” program would have some workers on the clock till midnight, then be available on call. The street workers are jointly administered by the city and the Boston Ten Point Coalition.

At a meeting in June, law enforcement authorities and church leaders warned gang members that violence would meet with tough sentencing. They also offered alternatives to gang activity. The approach had been tried before, but Ten Point Coalition Executive Director Rev. Jeffrey L. Brown said the newest group responded with “less bravado” and more interest in alternatives.

“This time around, the kids were really listening to us,” he said. “You’ve got a younger set of shooters than before,” he explained, “so they seem more apt to listen to people approaching them out on the street, who are out there to help them rather than put them in jail.”

Over the last three weeks, Brown says, street workers have helped make it possible for members of different gangs to spend time at Washington Park in Roxbury without conflicts. “They’re not looking to do anything,” he said. “They’re just trying to relax in the city.”

Along with the street workers, Brown credits community volunteers who walk through “hot spot” neighborhoods.

Less reassuring this year are the figures on Boston’s non-fatal shootings. As of July 19, the total number of all shootings this year was slightly higher than it was last year.

Given the fall-off in homicides without a decrease in shootings, the founder and director of the Louis D. Brown Peace Institute, Clementina Chery, says the reason might be neither the weather nor efforts of law enforcement.

“So people get shot but don’t get killed? Who gets credit for that?” she asked. “Hospitals are doing a better job in treating victims.”

Through May 25, the total number of non-fatal shootings for this year was 89, up from the figure for the same period last year by more than 50 percent. But, from May 25 through July 19 this year, the figure was 39, down from the same period last year by 35 percent.

The executive director of the Dorchester Youth Collaborative, Emmett Folgert, notes the recent change in shootings, and the kind of people involved.

“The gang stuff is down,” he says.

But Folgerrt says one reason could be fewer targets on porches and sidewalks for drive-by shooters – on account of the weather.

“The rain is our best friend,” he said.

But there have also been changing trends in arrests and convictions.

A spokesperson for Suffolk County District Attorney Daniel Conley, Jake Wark, says the conviction rate for homicide has improved over the past two years, while more people are being prosecuted on gun charges.

“That takes some players off the street longer than they used to after a gun arrest,” he said.

Folgert says the Boston Police have done “a lot of good work getting guns off the street.” So far, the Boston Police report arrests for all gun-related offenses have increased this year by 8 percent.

Chery says there should be more attention paid to the reasons for violence. Like other leaders of community-based programs, Chery and Folgert have described much violence as retaliatory and cyclical. But Folgert says a cycle of violence can be moderated by a cycle of weather.

“We’ve all heard that violence begets more violence,” he said. “Well, peace begets more peace.”