(CBS News) The beginning of summer means we can count on long hot days ahead and, of course, baseball. Heat is something that is dominating baseball today but not the kind of warmth that thermometers measure.
It's actually the heat that's coming across the plate. Major league fastballs sometimes come in at over 100 miles per hour.
The pitchers that throw them are called flamethrowers, and there are more of them in pro baseball now than ever before.
You may not see it during pre-game warm-ups, but the Seattle Mariners have three of the hardest-throwing pitchers in the big leagues, with an average fastball of nearly 96 miles per hour.
As a closer, Tom Wilhelmsen saves games for the Mariners. His 99 mph fastball saved his career. After six years away from the game bartending, his blazing speed at an open tryout got him back in the game.
"To have a few extra miles an hour helps quite a bit," he said. "You're able to miss a spot and get away with a little bit more, I think, if you know if you got some Aroldis Chapman kind of speed."
Chapman, or the Cuban Missile as he's known, clocked the fastest pitch in baseball history. Three seasons ago, Chapman blew away more than opposing hitters, when all 25 of his pitches in a game hit triple digits.
When he's at the mound, everyone is looking at the radar gun after every pitch, which adds some excitement when he comes in.
He's not the only one that can throw at these speeds.
"There is the general sense among the physiologists that a little faster than 100 miles an hour is as fast as a human being can throw a baseball," said Matt Futterman, a sports reporter at The Wall Street Journal who has followed the rise of baseball's flamethrowers. "But what we are seeing is that so many people being able to throw at those speeds."
Just 10 years ago, Billy Wagner was the only pitcher to throw 25 pitches in a season at 100 miles per hour. Last season there were seven. The website fangraphs.com is already asking who is going to throw the fastest pitch in 2013.
In 2003, just 20 pitchers threw at least 25 percent of their fastballs 96 mph or higher, and last year 62 pitchers hit that mark.
"If you have a guy who throws 90 he is going to get some attention, and if a guy throws 95 he is going to get a lot of attention," said Futterman.
He also said that this craze has not just stopped in the big leagues and has trickled down to the little leagues.
"You go to little league games and you see dads and moms holding radar guns as they watch their kids throw against the Maroon Monsters and the Red Raiders. And they come off the field saying, 'My kid was throwing 68 yesterday' or 'He was throwing 71' or 'He finally broke 75 and he is 13 years old,'" said Futternan.
Seattle's 22-year-old relief pitcher Carter Capps started his freshman year of college as a catcher, until it was suggested he try pitching. By graduation, Capp was throwing 97 mph. Last season, he led the majors with an average fastball of 98.
Now, the wonder is if batters can even hit a pitch moving that fast. Researchers at Louisville Slugger crunched the numbers, and a 104 mph pitch with a 5-foot stride takes about the same amount of time to reach home plate as the blink of an eye.
So if a batter blinks when the ball is released, he won't see the ball until it's in the catcher's mitt.