BOSTON -- Hellen Obiri defended her women's title in the Boston Marathon on Monday, outsprinting fellow Kenyan Sharon Lokedi down Boylston Street to win by 8 seconds.

Obiri, 34, is the first woman to win back-to-back Boston Marathons since 2005 and the sixth overall. She finished in 2:27:37.

"Defending the title was not easy," Obiri said. "Since Boston started, it's only six women [to have repeated]. So I said, 'Can I be one of them? If you want to be one of them, you have to work extra hard.'

"And I'm so happy because I'm now one of them. I'm now in the history books in Boston."

Two-time Boston champion Edna Kiplagat completed the Kenyan sweep, finishing another 36 seconds back.

On a day when sunshine and temperatures rising into the mid-60s left the runners reaching for water -- to drink, and to dump over their heads -- Obiri ran with an unusually large lead pack of 15 through Brookline before breaking away in the final few miles.

"I'm not giving up," Obiri said she told herself. "I'm not going to let this one go."

Obiri, who collected a gilded olive wreath and $150,000 from a total prize purse that topped $1 million for the first time, also won New York last year. She is one of the favorites heading into the Paris Olympics.

Emma Bates of Boulder, Colorado, finished 12th -- her second straight year as the top American. She found herself leading the race through the 30-kilometer mark, slapping hands as she ran past the Wellesley College students chanting her name before fading on the way out of Heartbreak Hill.

"I thought last year was crazy loud, but this year surpassed that completely," Bates said. "It was such a nice day for the spectators. Not so nice for the runners; it was pretty hot."

Nearly 30,000 runners participated in the 26.2-mile race. Sunny skies and minimal wind greeted the runners, with temperatures that rose into the 60s in late morning.