Food For Thought: Velocity vs. Temperature

Game One: Opening Day
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PitchFX guru Mike Fast posted a gem yesterday (no subs. req’d), looking at pitch velocity versus temperature. Surprisingly, at least to me, the relationship between fastball velocity and game-time temperature is pretty linear, with velo increasing by one mile an hour for every 37-degrees (or so) according to Fast. This graph shows that fastball velocity gradually increases early in the season before peaking in July in August, and the change is not insignificant. We’re talking about a difference of 1.5-2.0 mph from March/April to July.

Fast acknowledges that the study isn’t perfect, as adjustments for specific pitch types (two-seamer vs. four-seamer, etc.) and climate are needed, but the early data suggests that there is substantial correlation between fastball velocity and the weather. So yeah, stop sweating March/April radar gun readings.

Game One: Opening Day
ESPN's 50 Greatest Yankees
  • Joe R

    Makes sense. Warmer weather the muscle loosens up which allows you to produce more velocity.

    • AndrewYF

      I always thought more heat meant more grunting and farting. You can’t be a power pitcher without it.

    • pete

      that, and three months worth of pitching.

  • Mickey Scheister

    Jober and CC both lacked their normal FB speed today, so as it heats up, so does the heater! Nice, nice! So(ranio) looked like he had his heater working. I love me some opening day!

  • Lou

    Yeah, I wonder how much of this is because the pitchers peak later in the season vs he actual 1 meter temperature.

    I would like to see this data for just pitchers in a dome and compare.

    • ROBTEN

      I agree that there is a risk of correlation versus causation here. If it were weather alone, one would expect pitchers to throw several miles an hour faster in spring training than at the beginning of the season, but this in itself might not be enough since it wouldn’t account necessarily for types of pitches thrown.

      If I speculated, I would imagine that it is a combination of arm strength and weather, although more would have to be done to demonstrate causation either way and to isolate the extent to which weather is a leading contributor to velocity. For example:

      pitchers who pitched in winter leagues vs. those that didn’t
      pitchers who pitch in warm weather cities/domes vs. those that don’t
      pitchers who pitch in warm weather cities/domes and pitched in summer leagues vs. those that don’t/didn’t

      • Chris

        Agreed. I suspect a graph of the same statistic over the course of the season would tend almost identically.

      • Felix

        Yup. Yet another baseball study rife with bias. Do any of these geniuses hold a higher degree in mathematics, statistics, economics, etc?

  • Brandon

    I would say 2 MPH on a fastball is pretty big deal. 89 to 91 or 93 to 95 is a big difference

  • A.D.

    Most of the concern here has been Hughes’s velocity in spring training, which would be warm weather.

  • mike hc

    I assume bat speed would have a similar relationship.

  • Milty

    I can believe that temperature has some effect on pitch velocity but did they control for the number of starts and the number of starts from the first start?
    I wonder how much of this is due to how far removed the pitcher is from his first start. It may be that it generally takes pitchers a certain number of starts to hit peak velocity and then fatigue sets in and velocity drops.

  • ultimate913

    Just shows how scary Verlander can really be on a hot day. Dude was hitting 96 on a day like this.

    Scary pitcher is scary.

  • Andrew Cole

    A relationship like this is exactly what you’d expect based on the relationship between temperature and density of air. I bet going from 40 degrees to 100 degrees is not much different from going from sea level to Coors field. Exact same physics that makes those home runs soar farther in August in Texas than in Milwaukee in April. Is the gun measuring speed out of the pitcher’s hand, or speed crossing the plate?