The 25 heaviest days of the last three and a half years
By Alan Scott · Who makes this · Tijuana, Baja California ·
We sorted 1,266 days at San Ysidro from worst to best and kept the top 25. The interesting part isn't the numbers — it's what they have in common.
The five worst
| Date | Day | Actual | A normal day | Difference |
|---|---|---|---|---|
| March 24, 2023 | Friday | 195 min | 76 | +119 |
| October 15, 2025 | Wednesday | 190 min | 78 | +112 |
| March 10, 2024 | Sunday | 185 min | 106 | +79 |
| September 5, 2023 | Tuesday | 184 min | 81 | +103 |
| September 3, 2024 | Tuesday | 180 min | 86 | +94 |
Three hours and fifteen minutes was the worst. And look at fourth and fifth place: those are the Tuesdays after Labor Day. Which means that pattern isn't a tidy average — they are literally among the worst days on record.
Which weekday they land on
| Day | Days in the top 25 |
|---|---|
| Sunday | 9 |
| Monday | 6 |
| Tuesday | 6 |
| Saturday | 2 |
| Wednesday | 1 |
| Friday | 1 |
| Thursday | 0 |
Sunday, Monday and Tuesday account for 21 of the 25. And there is not a single Thursday.
In three and a half years, Thursday has never been among the worst days. If you have to pick a day for an errand on the other side and it genuinely doesn't matter which, that's Thursday.
Which month they land in
| Month | Days in the top 25 |
|---|---|
| July | 6 |
| June | 4 |
| December | 4 |
| March · May · August · September · October | 2 each |
| February | 1 |
| January · April · November | 0 |
Summer and December account for 14 of the 25. And January doesn't appear once, which lines up with it being the best month of the year.
The top two don't fit, and we're saying so
March 24, 2023 and October 15, 2025 are an ordinary Friday and an ordinary Wednesday. No holiday nearby, no long weekend, nothing. And they stand apart from the rest by 20 and 25 minutes.
The likely cause is a lane closure, an emergency or a special operation on those days. We don't know, and we're not going to invent it.
But they're useful for something, and it's the most valuable lesson in this article:
The line can blow up on an ordinary day, with no warning and no reason you could have anticipated. No average, no statistic and no forecast was going to save you from a 190-minute Wednesday.
That's why the number right now matters more than any prediction. Patterns help you plan the week; only the current number tells you whether today is one of those days.
What this data does NOT tell you
These are the worst 25 out of 1,266 — about 2% of days. They are not "how it usually is." An average day is 85 minutes, not 180.
It doesn't tell you the hour. All full-day averages.
And the top 25 is tilted by how much data exists. Since our data starts in late January 2023 and runs to August 2026, there are more complete Julys and Augusts than Januaries. It doesn't distort the result much, but it's honest to say it.
You might also want:
- Friday is the best day to cross
- The Tuesday after a U.S. holiday is the worst day
- The worst days of the year are December 15–23
Sources
Data: San Ysidro, General passenger vehicle lane, northbound. SANDAG, from U.S. Customs and Border Protection records. Period: January 29, 2023 to August 8, 2026 · 1,266 days. Method: all 1,266 days sorted by wait time. The "normal day" column is the median of days with the same weekday across that year. Retrieved: August 11, 2026.
We are not affiliated with CBP or SANDAG.
CHART · build spec
Same two charts as the Spanish version — see 6_CONTENIDO/articulos/06_los_dias_mas_pesados.md. 🔴 Do not re-derive the values.
Label translations only. 🔴 The rule that stays: Thursday's bar is drawn at zero, visible and labeled "0 · not once." The zero is the data — it cannot be omitted. Same for the months at zero.