FanGraphs Feature Focus: Weather Splits

For today’s FanGraphs Feature Focus, I’ll be taking a look at one of my favorite site features: our Weather Splits. Michael Baumann spotlighted these splits back in 2024, and the format of the page hasn’t changed since then. So while I’ll walk you through how the Weather Splits work and where to find them, I’ll mostly be showcasing some of the silly leaderboards they can help to generate.

To create the leaderboards in this piece, I toyed around with the Weather Split Ranges on the Splits tab of the Splits Leaderboard:

Those Weather Split Ranges aren’t mutually exclusive or siloed off from the rest of the splits. For example, by changing the Wind Speed filter and adding the Wind Direction sub filter, we can see which players have hit multiple home runs with the wind blowing in at 10 mph or more:

Bob Seger would be proud of Ryan Jeffers, who is currently on the IL after undergoing hamate surgery but still tops this leaderboard as the only player with a trio of homers against significant winds. If you click into the full leaderboard, you’ll notice that Auto PT is on:

When that’s the case, the leaderboard will smartly adjust the minimum playing time depending on how restrictive your search is, sometimes setting no minimum at all. You can always set your own minimum in the Filters section. The Temperature filter is even more straightforward to use, though here I’ll note that our filters don’t automatically eliminate indoor or retractable roof stadiums. That’s done with the Ballpark Type filter:

Applying those two filters in tandem, I made a list of the pitchers who’ve done especially well when it’s either chilly or flat-out cold, and they’re actually exposed to those elements:

While the ball doesn’t carry as well in cooler temperatures, it can also cause pitchers to experience grip troubles, even at a relatively balmy 57 degrees. But that hasn’t affected the pitchers on this leaderboard.

The Weather Splits are also a great excuse to take a crash course in barometric pressure, which I had to do in order to understand our various splits. Per Maximum Weather Instruments, which sells barometers and other pressure measurers, normal air pressure is considered 1,013.25 millibars. Anything above that is considered high pressure, so I set my minimum at 1,014. These relievers are the guys most frequently used in high-pressure situations… in both senses of the word:

Did I really do this research and make a whole leaderboard just so I could make an “Under Pressure” joke? I choose to exercise my Fifth Amendment rights, Your Honor.

I made leaderboards for these three splits, but we’ve got plenty more within the Weather tab of the Splits Leaderboard. Beyond the ranges for temperature, pressure, and wind, you can also set ranges for air density and elevation. The Ballpark Type and Weather tabs at the top also include some binary filters that you can combine (e.g., rain and drizzle, or fog and haze):

As with ballpark type and leverage, the weather ranges can be combined with both each other and the binary weather filters. For instance, you could look at high winds in warmer weather only, or rain in colder weather only.

Our Weather Splits are available going back to 2010, and the entirety of the Splits Leaderboard can be accessed regardless of whether you’re a FanGraphs Member. But if you want to export to Excel to more easily compare player performance across splits, you have to be a Member. If you’d like to sign up for a Membership, you can do so here.