The Core Premise
Weather conditions at game time have a measurable, consistent effect on MLB scoring, but that effect is park-specific, direction-dependent, and easy to misread without the right framework. A 15 mph wind at Wrigley Field blowing out to center is not the same as 15 mph at Oracle Park. Raw forecast numbers without park context are noise.
OVERcast is built around the idea that each park has its own historical fingerprint: how scoring changes as temperature rises, how home run rates shift when wind blows in versus out, how humidity at sea level affects carry differently than dry mountain air. That fingerprint is built from actual game results, not assumptions.
The Data Foundation
The historical dataset covers over a decade of MLB results, matched to park-level weather conditions at game time. Each game record includes final run totals, home run counts, strikeouts, the specific ballpark, and the weather conditions present at first pitch: temperature, dew point, wind speed, and wind direction relative to the field's orientation.
Each morning, the engine pulls the latest National Weather Service forecast for each ballpark's exact coordinates and game time, then scores today's slate against those conditions using the park's historical performance profile.
The Four Weather Variables
Warmer air is less dense, which means less drag on a batted ball. The effect is real and measurable: at the same exit velocity and launch angle, a ball hit in 90°F weather carries noticeably farther than the same ball hit in 50°F conditions. OVERcast bins game-time temperature and compares scoring rates within each park's historical dataset to quantify how much each park amplifies or dampens this effect.
Contrary to intuition, humid air is actually less dense than dry air. Water vapor (H₂O, molecular weight 18) displaces heavier nitrogen and oxygen molecules (28 and 32). High dew points slightly favor hitter-friendly conditions, though the effect is secondary to temperature and wind. OVERcast uses dew point rather than relative humidity because dew point is absolute and doesn't change with temperature fluctuations throughout the day.
Wind is the highest-variance weather factor in baseball. Strong wind amplifies every other condition: it can turn routine fly balls into home runs or rob well-struck balls of 40 feet of carry. The effect is nonlinear: a 20 mph wind out to right-center at Wrigley produces more scoring variance than a 20 mph wind at a wind-sheltered park like Dodger Stadium. Wind speed is evaluated in conjunction with direction for this reason.
Direction is where most weather models break down. A raw "10 mph NW wind" means nothing without knowing the park's field orientation. OVERcast maps each park's home plate-to-center field bearing and converts the forecasted wind direction into a field-relative angle: blowing out, in, across, or from dead center. The historical dataset is then filtered by this angle to build a statistically grounded picture of how that specific wind pattern affects scoring at that specific park.
Park Factors & Sample Depth
Two parks can face identical weather conditions and produce very different scoring environments. Oracle Park's marine layer and deep dimensions suppress fly balls even on warm days. Coors Field's altitude amplifies carry in all directions. Camden Yards' asymmetric wind tunnel created by the warehouse in right changes with the breeze.
Each park's historical pool is filtered to conditions similar to today's forecast. It is not compared across the whole dataset. A hot, calm day at Great American Ball Park is scored against only the hot, calm games played there, not all games ever played in Cincinnati.
Every card on OVERcast shows a sample count: the number of historical games that match today's conditions at that park. Larger samples indicate stronger statistical confidence. Thin samples (common for unusual weather conditions) are surfaced transparently so you can weigh confidence appropriately.
Retractable Roof Parks
Parks with retractable roofs (Chase Field, Globe Life Field, Minute Maid Park, T-Mobile Park, and others) are handled separately. A closed roof effectively neutralizes weather as a variable. OVERcast treats these parks as two distinct environments: one historical pool for open-roof games, one for closed.
On the slate, retractable parks show a roof toggle. Flipping it open reveals the weather-adjusted analysis for the open-roof historical pool, which is most useful once roof status is confirmed open, or when you want to compare the two environments side by side. By default, the card shows the closed-roof baseline since roof status isn't always confirmed in advance.
What OVERcast Surfaces
For each game on today's slate, OVERcast shows three park-adjusted metrics relative to the historical league average:
Home Run factor: how today's conditions at this park compare historically to the baseline HR rate, expressed as a percentage above or below average.
Run scoring factor: the same framework applied to total runs, useful for over/under analysis on game totals.
Strikeout factor: whether conditions favor pitchers or hitters. Cool, dense air and wind blowing in can suppress offense in ways that show up more clearly in K rate than in run totals.
Each metric is paired with the current O/U line so you can immediately evaluate whether the market has priced in the weather conditions for that day.
What OVERcast Is Not
OVERcast is a weather analysis tool, not a pick service. It surfaces environmental edges: situations where conditions meaningfully shift the historical scoring distribution at a given park. What you do with that information is your call.
It does not model pitching matchups, lineup construction, bullpen usage, injuries, or travel fatigue. Weather is one input among many in a full game model. OVERcast is built to answer one specific question: what do weather conditions say about scoring potential at this park today. It answers it faster and more rigorously than doing the research manually.
See Today's Slate
Weather-adjusted analysis for every eligible MLB game, updated each morning before first pitch.
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