April Baseball: Fewer Home Runs, but Not Always Fewer Runs

Across 1,389 April games at open-air parks from 2021–2025, there were 2.07 home runs per game, compared with 2.37 in 7,333 May–September games—about 13% fewer. The April home-run rate was lower in all five seasons.

Total scoring is a less tidy story: 8.68 runs in April versus 9.04 later. Four seasons followed that direction; 2023 did not. If you came looking for “April always means low scores,” that exception matters.

Our temperature guide explains the physics. This page asks a different question: does the early-season pattern survive when we compare the same parks in the same years?

April’s played games averaged 59.3°F; May–September averaged 75.1°F. The home-run curve builds toward July and eases into September. The scoreboard does not follow quite as neatly: May and September both sit close to 8.85 runs.

The raw April difference is −0.30 home runs per game (Welch p < 0.0001; 95% CI −0.39 to −0.21; Cohen’s d −0.18), and −0.36 runs (p = 0.0064; CI −0.62 to −0.10; d −0.08). Those are small effects at individual-game level, not a prediction for tonight’s result.

A league-wide average can change simply because different parks host different numbers of games. To reduce that distortion, we calculated April minus May–September separately for each park-season, then averaged the 110 paired comparisons equally.

The resulting difference was −0.32 home runs and −0.43 runs per game. April was about 15.8°F cooler within those comparisons. This controls which park and which season we compare, but it does not control opponents, pitching, wind or lineups.

Exploratory paired t intervals assume independent park-season differences. Parks recur across years and teams share league conditions, so these intervals may understate uncertainty. They are not causal estimates or cluster-robust evidence. Raw game comparisons above use Welch–Satterthwaite tests instead.

April 2022 was the sharpest slump here: 1.71 home runs and 7.94 runs per game. That is the season ESPN examined through the baseball itself and the scoring drought. Weather was not the only explanation being considered.

Then came April 2023: fewer home runs than later that year, but more total runs—9.43 versus 9.29. A walk and a pair of singles can do the work that one long ball did not. Our records cannot tell us which mechanism caused that season’s reversal.

Nor is a recent pattern a timeless law. Nate Silver’s 2007 Baseball Prospectus analysis found slightly higher scoring in the first three weeks across 1957–2006. Its years, opening-week window and population differ from ours; that is a reason to specify the sample, not declare the old finding wrong.

Cleveland, Chicago and Minneapolis lead this played-game temperature list. Yet Progressive Field’s pooled home-run rate rounds to 2.09 in both windows. Coldest does not automatically mean the largest seasonal home-run decline.

The equal-season comparison also goes the other way at Angel Stadium and Petco Park. Angel Stadium’s April difference is +0.34 HR per game; Petco’s is +0.07. These park checks are exploratory and unadjusted for multiple comparisons—we do not treat the biggest differences as proven park-specific effects.

Within April itself, games below 50°F averaged 1.71 home runs (256 games), against 2.44 at 70–79°F (196 games). The raw gap is −0.73 (Welch p < 0.0001; CI −1.03 to −0.42; d −0.46). Runs were 8.27 versus 9.93 (p = 0.0003; CI −2.57 to −0.76; d −0.35). Different parks and teams populate those groups; this is context, not a controlled weather experiment.

Start with the forecast, not the calendar. A 74°F April afternoon belongs in a different conversation from a 44°F night. The American Meteorological Society’s explainer describes why colder air adds drag and discusses evidence on temperature and offensive performance.

Then put the wind in the park. Wind blowing toward the outfield is not the same as wind blowing in from it. At Wrigley Field, that distinction can matter more than the season’s average temperature. At coastal parks, check the actual conditions rather than assume that the marine layer guarantees a dead night.

And check the roof. These numbers come only from fixed open-air parks. They are not evidence about a game under a closed retractable roof; see the MLB roof guide.

For anyone checking a total, fewer observed runs are not the same thing as an overlooked price. We have not tested an April betting strategy here. Check MLB game-time weather as one input alongside the matchup, not as a pick.

Snapshot queried 12 October 2026: 8,888 records from our MLB game-conditions archive, 2021–2025, with roof type “Open.” All 8,888 unique game IDs matched MLB Stats API regular-season games marked Final, with runs, home runs and archived Open-Meteo temperature present. April (1,389) and May–September (7,333) form the 8,722-game comparison; 166 March/October games are outside that window.

Month uses MLB’s official baseball date, not the UTC timestamp: a late West Coast game should not silently become a May game in this analysis. Venue name changes are grouped by the stored park identifier. Oakland and Sutter Health are separate physical parks. The 2026 archive stopped in early September when checked, so we excluded that incomplete season.

This is the matched archive, not a claim of a league-wide weather census. Postponed games are absent until played; retractable and fixed-roof venues are excluded. Weather is an archived game-time estimate, not an instrument reading on the field. We do not adjust for humidity, wind, team strength, rule changes, pitching or ball construction.

Welch–Satterthwaite tests compare raw groups; Cohen’s d uses pooled standard deviation. The separate park-season analysis uses paired differences, paired t intervals and dᶻ. Repeated parks and common league conditions limit that inferential calculation. Comparisons with fewer than 40 observations per group are directional only; Sutter Health has just 14 April games and is not included in the featured five-park table.

This analysis has not been independently reviewed. Published by the OverUnderWeather Research Desk. Read our editorial policy and corrections log. Historical discussion: The Hardball Times, “The Truth About April Home Runs” (2007).