New York (CNN) -- As weekend temperatures soared over 90 degrees Fahrenheit, New York City saw a sudden increase in shootings, with 26 people felled by bullets in 72 hours -- seven fatally.
"When we have hot temperatures, we see that the crime rate seems to go up," New York City Mayor Michael Bloomberg said Monday.
But Bloomberg emphasized that for the year, shootings are down in the city -- 127 since January 1, which is 40 less than the same period in 2012.
"One shooting is one too many, but last week we had the fewest shootings in a decade, including this weekend's shootings," Bloomberg noted.
A professor says the heat index and the crime rate can connect.
"Lifestyle differences exist between cold weather and warm weather," says James Alan Fox, a professor of Criminology, Law and Public Policy at Northeastern University in Boston.
Fox has conducted research on the possible connection between temperature and crime. His findings illustrate how these lifestyle differences can contribute to varying levels of violent crime.
"In cold weather, particularly in blizzards, people stay indoors, and the violent crime rate is lower. When the weather is warm, people are interacting more with others, be they friends, family, or strangers, so there are increased opportunities for conflict," Fox says.
Fox says this trend continues except when it gets incredibly hot, so unbearable that even criminals become lethargic.
"When it gets to be in the high 90s, especially over 100 degrees, people just go indoors and look for air conditioning," Fox said.
However, drawing any conclusions about this past weekend may be premature, says Professor Jon M. Shane, assistant professor in the Department of Law, Police Science, and Criminal Justice Administration at John Jay Criminal College.
"I would not put too much emphasis on a single spike in weather and the uptick shootings," Shane said. "The reality is that you do not have enough information from this single episode to conclude that hot weather is related to increases in crime--specifically shootings, in this case."
In November 2012, New York City logged a record-breaking "murder-free Monday" when there was not a single reported slaying, stabbing, shooting or knifing in any of the five boroughs, according to the New York Police Department.
"It is unusual in a city of 8 million people, but we never read that much into one day," said Deputy Police Commissioner Paul Browne, who said it was the "first time in memory" that the city had such a lull in violent crime.
At the close of 2012, Bloomberg hailed New York City the "safest big city in America," giving the NYPD credit.
"The fact that the safest big city in America is safer than ever is a testament to the hard work and determination of the men and women who put their lives on the line for us every day -- and it also reflects our commitment to doing everything possible to stop gun violence," Bloomberg said.
CNN's Chris Boyette and Adam Reiss contributed to this report.