CIM 2026: Cold, Damp, and Historically Fast — What the Data Says

California International Marathon has quietly become one of the most productive BQ courses in the country, sending at least 27.4% of its field to Boston qualifying times in every edition since 2021. The 2025 race, run in cold and nearly still air, pushed that figure to 30.2% — the highest of any edition in the dataset — while the field median dropped to 3:43:13, nearly seven minutes faster than the 2019 benchmark of 3:56:55. December in Sacramento delivers.

By the numbers

The field has grown from 7,470 finishers in 2019 to a peak of 9,182 in 2023, then settled to 8,168 in 2025 — still a substantial field for a point-to-point road marathon. Women made up roughly 37% of finishers in 2025 (3,031 of 8,168), a share that has held relatively consistent across editions. The median has improved meaningfully over six years: men's median moved from 3:46:42 in 2019 to 3:33:45 in 2025; women's from 4:11:24 to 3:56:41. Whether that reflects a sharper, more BQ-motivated field self-selecting into CIM or simply better conditions in recent years — or both — the trajectory is real.

Where the course bites

CIM's net 335-foot descent is not evenly distributed, and the fade curve from 2025 shows exactly where the course extracts its toll.

The field runs its fastest median segment between miles 3.1 and 6.2 — a stretch that also captures the steepest early descent (-46 ft in the 5–10K chunk after an opening -111 ft). Pace holds reasonably steady through the half, then the course turns honest. From 30K onward, the median slows by 40 seconds per mile between miles 18.6 and 24.9 — a 8:31 to 8:52 deterioration — before a modest recovery in the final 1.3 miles (8:35). That late lift likely reflects the flat 40–42K finish segment rather than any genuine re-acceleration by the field.

Pacing reality check

Positive splitting is the norm at CIM, not the exception. In 2025, 63% of the field went out faster than they came back — the lowest positive-split rate in the dataset, and a meaningful improvement over 85% in both 2019 and 2023. The average second-half slowdown has also compressed dramatically: from 12% in 2019 and 11.8% in 2023 to 6.3% in 2025. The coldest, calmest editions correlate with the best pacing. In 2023 (53–63°F, overcast), only 554 runners ran negative splits; in 2025 (36–46°F, near-still), that number climbed to 1,479.

The weather question

The 2026 forecast — 38–48°F, mist, wind ~8 mph, 93% humidity — sits closer to the 2022 profile (46–56°F, light rain, wind ~7 mph, 80% humidity) than to the near-ideal 2025 conditions. In 2022, the positive-split rate was 81% and the average second-half slowdown was 10.8%; the median finished at 3:49:47. The 8 mph wind is the most significant variable: 2025's ~3 mph wind coincided with the fastest median in the dataset. Mist and higher humidity alone haven't historically collapsed performance, but the combination of moisture and the strongest forecast winds since 2019 (9 mph, 12% slowdown) warrants attention.

What it takes

In 2025, cracking the top 10% required finishing under 2:50:34; top 25% demanded sub-3:11:22. The field median was 3:43:13. Boston qualifier count reached 2,469 — the second-highest total across all editions despite a smaller field than 2023.

What to watch

The BQ rate has climbed from 25.2% in 2019 to 30.2% in 2025 — can it hold above 30% in windier, wetter conditions? The 2022 rain year produced a 28.9% BQ rate, which suggests the floor may be higher than it once was. The men's median has improved by 12+ minutes since 2019; whether that trend continues or plateaus will be visible in how the 25th-percentile cutoff moves relative to 3:11:22. And with field size down from its 2023 peak, watch whether 2026 sees a rebound toward 9,000 finishers or a continued consolidation around the 8,000-runner mark.