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San Ysidro climate
Typical historical weather for San Ysidro, United States, averaged across 10 years of hourly climate data. Pick a date for a specific day.
Data last updated: 31 December 2025
Want today's actual conditions instead? See the current forecast for San Ysidro. Planning a garden? See the gardening & growing season planner. Or browse the 365-day climate calendar.
Annual average
18.8°C
across all months
Warmest month
35.5°C
Jul average high
Coolest month
1.2°C
Jan average low
Annual rainfall
183mm
total per year
San Ysidro is typically hottest in July and coolest in January, a swing of about 34.3°C across the year. About 44% of annual rainfall falls in the three wettest months (August is typically wettest, April driest).
Monthly averages
Average daily high/low temperature (band) and monthly rainfall (bars).
| Month | Avg high | Avg low | Rainfall | Wet days | Humidity | Wind | Cloud | Solar |
|---|---|---|---|---|---|---|---|---|
| Jan | 13.6°C · record 19.2°C–21.8°C | 1.2°C · record -7.9°C–-3.6°C | 11mm | 3 | 44% | 2.7 m/s | 31% | 3.8 kWh/m² |
| Feb | 17.4°C · record 22.3°C–27.3°C | 3.7°C · record -8.7°C–0.6°C | 10mm | 3 | 36% | 3.1 m/s | 34% | 4.8 kWh/m² |
| Mar | 21.2°C · record 25.6°C–31°C | 7.4°C · record -1.4°C–3.5°C | 10mm | 2 | 30% | 3.7 m/s | 35% | 6.2 kWh/m² |
| Apr | 25.9°C · record 29.8°C–33.3°C | 11.4°C · record -0.7°C–6.9°C | 3mm | 1 | 22% | 3.8 m/s | 25% | 7.6 kWh/m² |
| May | 30.5°C · record 32.6°C–37.3°C | 15.7°C · record 5.4°C–12.7°C | 4mm | 1 | 20% | 3.6 m/s | 19% | 8.3 kWh/m² |
| Jun | 35.3°C · record 37°C–42.1°C | 21.1°C · record 11.5°C–18.4°C | 19mm | 3 | 26% | 3.2 m/s | 30% | 8.1 kWh/m² |
| Jul | 35.5°C · record 37.9°C–42°C | 22.7°C · record 18.4°C–21.2°C | 23mm | 6 | 37% | 2.5 m/s | 41% | 7.6 kWh/m² |
| Aug | 34.1°C · record 36.1°C–42.5°C | 21.8°C · record 16.9°C–20.7°C | 36mm | 7 | 42% | 2.3 m/s | 43% | 6.9 kWh/m² |
| Sep | 31.2°C · record 33.7°C–38.7°C | 18.4°C · record 9.5°C–16°C | 21mm | 5 | 42% | 2.5 m/s | 29% | 6.1 kWh/m² |
| Oct | 25.9°C · record 28.8°C–33.7°C | 12.7°C · record -2.4°C–9.8°C | 22mm | 3 | 40% | 2.6 m/s | 23% | 5.1 kWh/m² |
| Nov | 19.3°C · record 24.3°C–28.7°C | 6.3°C · record -3.6°C–2.8°C | 12mm | 2 | 42% | 2.6 m/s | 32% | 3.9 kWh/m² |
| Dec | 15°C · record 19.5°C–23.7°C | 2.7°C · record -6.1°C–-0.3°C | 13mm | 2 | 45% | 2.4 m/s | 35% | 3.3 kWh/m² |
"Avg high"/"Avg low" is the mean daily high/low for that month, averaged across every year on file. The "record" figure alongside it is a different statistic — the single hottest (or coldest) hour ever recorded during that month across all years — so it can sit above or below the average and does not describe the average's year-to-year spread. A "wet day" is any day with at least 1.0mm of rain.
Year to year
Annual average temperature, 2016–2025.
Across these 10 years, the annual average has moved by about +0.4°C per decade. That’s a short window for a reliable long-term climate trend — treat it as indicative, not definitive.
Annual rainfall has moved by about -67.76mm per decade over the same period.
2025 (the most recent year on file) averaged 19.3°C, above the 9-year baseline of 18.8°C by 1.04 standard deviations.
Typical extremes per year
Rainy days
38.1 days
≥1.0mm rain
Heavy rain days
0.8 days
≥20mm rain
Extreme heat days
3.5 days
daily high ≥40°C
Frost days
27.2 days
daily low ≤0°C
Averaged across 10 years on file. Thresholds match PastClimate's data pipeline definitions — see data & sources.
Records on file
Ranked across 10 years of data currently on file (2016–2025).
Hottest day
42.5°C
6 August 2023
2023 was 0.91 SD above the 9-year average that year
Coldest day
-8.7°C
15 February 2021
2021 was 0.94 SD below the 9-year average that year
Wettest day
35.4mm
13 August 2021
2021 was 0.94 SD below the 9-year average that year
Windiest day
10.4m/s
13 March 2019
2019 was 1.77 SD below the 9-year average that year
See the detail: San Ysidro on 13 August 2021.
Nearby cities
Frequently asked questions about San Ysidro's climate
What is the hottest month in San Ysidro?
July is typically the warmest month in San Ysidro, with an average high of 35.5°C. January is typically the coolest, averaging 1.2°C overnight.
How much does it rain in San Ysidro?
San Ysidro gets about 183mm of rain a year on average, with roughly 44% of it falling in the three wettest months (August is typically the wettest, April the driest).
How many extremely hot or cold days does San Ysidro have?
On average, San Ysidro sees about 3.5 day(s) a year at or above 40°C and about 27.2 day(s) at or below 0°C, based on 10 years of data.
Is San Ysidro getting warmer?
Across the 10 years on file (2016–2025), the annual average temperature has moved by about +0.36°C per decade. That's a short window for a reliable long-term climate trend — treat it as indicative, not definitive.
What is the hottest day on record for San Ysidro?
The hottest day on file is 6 August 2023 at 42.5°C, out of 10 year(s) searched.
Data & provenance
↓ Download monthly CSVData source & coverage — ERA5 reanalysis, 2016–2025 (10 years)details
- Source
- ERA5 reanalysis, accessed via the Copernicus Climate Change Service (C3S) Climate Data Store
- Data type
- Reanalysis — a physically consistent reconstruction combining a forecast model with historical observations, not a live station reading or a forecast
- Coverage
- 2016–2025 (10 years) for United States
- Location
- San Ysidro — 32.250°, -106.750°, ERA5 grid cell center, 12.6 km from requested point
- Time zone
- America/Denver
- What's shown here
- Monthly and annual averages, and dated extreme-value records, derived from an hourly base record.
- Spatial resolution
- 0.25° (~25 km) distributed grid — ERA5's native model resolution is finer; this is the publicly distributed regridded product
- Version / refreshed
- Methodology v2026.07 · data last refreshed December 31, 2025
- Limitations
- A model reconstruction, not a station observation — hyper-local extremes (a single storm cell, an urban heat pocket) can differ from a nearby gauge. See the full methodology.
- Attribution
- Generated using Copernicus Climate Change Service information
Cite this data
PastClimate (2026-07-20). Historical climate data for San Ysidro, United States (32.25°N, 106.75°W), derived from ERA5 (Hersbach et al., 2023, Copernicus Climate Change Service). Retrieved from https://www.pastclimate.com/
PastClimate. (2026). Historical climate data for San Ysidro, United States [Data set]. Derived from ERA5 (Copernicus Climate Change Service). Retrieved July 20, 2026, from https://www.pastclimate.com/
"Historical Climate Data for San Ysidro, United States." PastClimate, derived from ERA5 (Copernicus Climate Change Service), July 20, 2026, www.pastclimate.com.
@misc{pastclimate,
author = {PastClimate},
title = {Historical climate data for San Ysidro, United States},
year = {2026},
note = {Derived from ERA5 (Hersbach et al., 2023), Copernicus Climate Change Service. Accessed 2026-07-20},
url = {https://www.pastclimate.com/}
}Notice something wrong with this data? Report a data issue.