The number of homicides, robberies and assaults have dropped significantly in the District over the past six months, a hopeful signal for police and city officials trying to build on modest crime declines last year after a spike in killings in 2015.

Violent crime is down 26 percent from the same period in 2016, led by a 33 percent decline in robberies. Homicides are down 15 percent, from 61 at this time in 2016 to 52 so far this year. Violent crime went down 10 percent in 2016 compared with 2015.

Members of law enforcement remain cautiously optimistic as the hot summer starts and worries mount that youths with idle time and little supervision could get into trouble over the lengthy holiday weekend.

“Summer months are a particularly challenging time,” said D.C. Council member Charles Allen (D-Ward 6), who is chairman of the public safety committee. He used those words to open a hearing Monday on whether D.C. police and other agencies are prepared for the summer.

Allen and other council members questioned an assistant police chief, a deputy mayor, and the director of Parks and Recreation over the spending of grant money, recreation center hours, job programs and whether the resources offered to teens and young adults are properly integrated and target those who need help the most.

D.C. Police Patrol Chief Lamar Greene said the drop in robberies has helped drive the drop in overall crime, and he credited a task force set up in 2015 on targeting criminals shortly after attacks, and sometimes even moments before potential crimes.

“I think this is something we will have for the foreseeable future,” Greene testified. He also said a focus on seizing illegal guns has contributed to the drop.

Greene said police commanders studied homicides and shootings from 2015 and came to no different conclusions now then they had at the time: the 2015 spike in homicides was the result of petty disputes settled in the heat of the moment by people carrying guns. That year ended with 162 homicides, up from 105 in 2014. There were 135 homicides in 2016; the city reached a 50-year low with 88 homicides in 2012.

Greene noted that police this year are continuing what is called the Summer Crime Prevention Initiative, where extra resources are poured into select neighborhoods where crime remains high. The plan calls for more police targeting guns and illegal drugs, but also more programs, community walks, medical help and counseling.

“Its goal is to engage with community residents in order to build and deepen trusting and respectful relationships,” said Kevin Donahue, the deputy mayor for public safety and justice. Throughout the city, Donahue said, the mayor’s Summer Youth Employment Program has placed 13,000 young adults in jobs.

In 2015, Mayor Muriel E. Bowser’s first year in office, more than one-third of District residents named crime the biggest problem, ahead of the economy and schools. A new Washington Post poll released last week showed that affordable housing — 19 percent — has replaced crime — at 13 percent — as the No. 1 concern for District residents.

One of those polled, Allison Kenny, 26, is a budget analyst for a nonprofit organization who lives on Capitol Hill. In 2014, she said, her apartment was burglarized when she lived on the H Street corridor.

Today, she said the city feels like a much safer place, in part because of a heavy presence of street officers. “There’s just an overwhelming amount of cops in this city, in a good way,” she said. “I think that’s good. I never feel unsafe.”

Peter Jamison contributed to this report.