CIM's Net Downhill Hides a Fade Problem That Catches Most of the Field

California International Marathon is one of North America's most prominent Boston Qualifier courses — 335 feet of net downhill, a December date that usually delivers cool temperatures, and a field that historically runs fast. But the data from six prior editions tells a more complicated story: the vast majority of runners slow down in the second half, and conditions in 2026 are shaping up to be among the most challenging the race has seen.

By the numbers

The full-field editions — 2019 through 2023 — ranged from 7,470 to 9,182 finishers, with 2023 representing the record participation referenced in the race notes. Median finish times across those years clustered tightly: 3:49:11 to 3:56:55, with men's medians between 3:38 and 3:47 and women's medians between 4:01 and 4:11. The 2024 and 2025 datasets contain only 10 and 7 finishers respectively and are not representative of the full field; the large-field editions are the meaningful baseline for what CIM looks like at scale.

Where the course bites

The elevation profile is deceptive. The opening 5K drops 111 feet — the steepest descent on the course — which can pull runners out too fast before the course flattens and even climbs slightly between 10K and 15K (+17 feet). The bulk of the remaining descent is spread across the middle and late miles, but the final 7K is essentially flat: the 35–40K chunk loses just 1 foot, and the last 2K is dead even. There is no late downhill reward to rescue a fading runner.

Checkpoint	Elevation Change
0–5K	−111 ft
5–10K	−46 ft
10–15K	+17 ft
15–20K	−84 ft
20–25K	−20 ft
25–30K	−43 ft
30–35K	−44 ft
35–40K	−1 ft
40–42K	0 ft

Pacing reality check

Positive splits are the norm at CIM. Across the full-field editions, between 72% and 85% of finishers ran the second half slower than the first. The average second-half slowdown ranged from 8.2% (2021) to 12% (2019). Even in 2021 — the best pacing year on record, with 1,012 negative splits — nearly three in four runners still faded. The 2023 edition saw an 11.8% average slowdown across 9,182 finishers, meaning a runner on pace for 3:30 at halfway was finishing closer to 3:54. The early downhill is almost certainly a factor: the 111-foot drop in the first 5K invites an aggressive opening that the flat finish cannot support.

The weather question

CIM has historically benefited from cool December mornings. The most favorable recent conditions came in 2021 (47–57°F, broken clouds, 68% humidity), which also produced the best pacing outcomes — lowest positive-split share at 72% and the smallest average slowdown at 8.2%. Wetter, windier editions fared worse: 2019 (light rain, 9 mph wind, 90% humidity) produced a 12% average slowdown and a median of 3:56:55, nearly eight minutes slower than the 2021 and 2023 medians.

The 2026 forecast — 38–48°F, mist, ~43°F at the start, wind ~8 mph, 93% humidity — most closely resembles 2019 and 2022 (both rainy, windy, high-humidity years) rather than the faster, clearer editions. Based on prior patterns, that combination correlates with the higher end of the fade range and slower overall medians.

What it takes

From the full-field editions, the top 10% cutoff has ranged from 2:51:26 to 2:54:46. Breaking into the top 25% has required finishing between 3:14:26 and 3:19:23. The median finish has sat between 3:49 and 3:57 depending on conditions. Men's winning times have been remarkably consistent: 2:11:00 to 2:13:35 across 2019–2023.

What to watch

Whether 2026 matches or surpasses the 2023 record field of 9,182 finishers is the headline participation question. The trend from 2019 through 2023 showed steady growth, and a sixth consecutive December running draws on that momentum.

The weather sets up as a potential drag on times. If the mist and 93% humidity hold, the historical analogue is 2019 — the slowest median of any full-field edition and the highest average fade. Whether the field adjusts its opening pace given the early downhill and the damp conditions will determine how close the 2026 median lands to 3:49 or to 3:57.

Finally, the gender split in pacing is worth watching. Women's medians have consistently been faster relative to men's in terms of fade management across several editions, and with women comprising roughly 43–44% of full-field finishers in recent years, their share of any negative-split cohort will be a telling signal.