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Bostonia climate
Typical historical weather for Bostonia, United States, averaged across 10 years of hourly climate data. Pick a date for a specific day.
Want today's actual conditions instead? See the current forecast for Bostonia. Planning a garden? See the gardening & growing season planner. Or browse the 365-day climate calendar.
Annual average
17.3°C
across all months
Warmest month
27.5°C
Aug average high
Coolest month
8.8°C
Jan average low
Annual rainfall
351mm
total per year
Bostonia is typically hottest in August and coolest in January, a swing of about 18.7°C across the year. About 56% of annual rainfall falls in the three wettest months (March is typically wettest, July 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 | 17.9°C · record 20.9°C–30.1°C | 8.8°C · record 3.5°C–7°C | 66mm | 7 | 65% | 2.3 m/s | 48% | 3.3 kWh/m² |
| Feb | 18.2°C · record 20.2°C–30.8°C | 9°C · record 2.9°C–7°C | 62mm | 7 | 64% | 2.3 m/s | 43% | 4.3 kWh/m² |
| Mar | 18°C · record 20°C–28.7°C | 10°C · record 4.4°C–7.5°C | 68mm | 9 | 71% | 2.4 m/s | 52% | 5.2 kWh/m² |
| Apr | 20.2°C · record 23.2°C–34.7°C | 11.9°C · record 5.1°C–10°C | 22mm | 5 | 68% | 2.3 m/s | 46% | 6.7 kWh/m² |
| May | 20.5°C · record 21.3°C–31.1°C | 13.6°C · record 8.8°C–12.1°C | 16mm | 3 | 71% | 2.4 m/s | 53% | 7.2 kWh/m² |
| Jun | 23.8°C · record 25.1°C–36.9°C | 15.8°C · record 12°C–14.2°C | 2mm | 1 | 69% | 2.1 m/s | 41% | 8 kWh/m² |
| Jul | 26.5°C · record 27.6°C–37.6°C | 18.4°C · record 14.6°C–17.1°C | 2mm | 1 | 69% | 2.1 m/s | 36% | 7.8 kWh/m² |
| Aug | 27.5°C · record 30.7°C–34°C | 19.2°C · record 15.8°C–18.9°C | 6mm | 0 | 68% | 2 m/s | 31% | 7.2 kWh/m² |
| Sep | 26.6°C · record 30°C–38.2°C | 18.3°C · record 11.4°C–16.4°C | 10mm | 2 | 67% | 2 m/s | 34% | 6 kWh/m² |
| Oct | 24.9°C · record 29°C–37.7°C | 15.2°C · record 9°C–13.3°C | 11mm | 2 | 61% | 1.9 m/s | 32% | 5 kWh/m² |
| Nov | 22°C · record 23.9°C–33.3°C | 11.7°C · record 6.8°C–10.1°C | 34mm | 4 | 57% | 2 m/s | 38% | 3.8 kWh/m² |
| Dec | 18.8°C · record 22.6°C–27°C | 9.5°C · record 4°C–7.1°C | 52mm | 5 | 62% | 2.1 m/s | 46% | 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 -1.3°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 +7.27mm per decade over the same period.
2025 (the most recent year on file) averaged 17°C, below the 9-year baseline of 17.4°C by 0.69 standard deviations.
Typical extremes per year
Rainy days
43.8 days
≥1.0mm rain
Heavy rain days
4.5 days
≥20mm rain
Extreme heat days
0 days
daily high ≥40°C
Frost days
0 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
38.2°C
6 September 2020
2020 was 1.23 SD above the 9-year average that year
Coldest day
2.9°C
24 February 2022
2022 was 0.32 SD above the 9-year average that year
Wettest day
58.8mm
27 February 2017
2017 was 1.28 SD above the 9-year average that year
Windiest day
7.4m/s
22 February 2023
2023 was 1.94 SD below the 9-year average that year
See the detail: Bostonia on 27 February 2017.
Nearby cities
Chula Vista
Same ERA5 grid cell
El Cajon
Same ERA5 grid cell
National City
Same ERA5 grid cell
La Mesa
Same ERA5 grid cell
Santee
Same ERA5 grid cell
La Presa
Same ERA5 grid cell
Want a side-by-side view instead? Compare Bostonia with another city.
Frequently asked questions about Bostonia's climate
What is the hottest month in Bostonia?
August is typically the warmest month in Bostonia, with an average high of 27.5°C. January is typically the coolest, averaging 8.8°C overnight.
How much does it rain in Bostonia?
Bostonia gets about 351mm of rain a year on average, with roughly 56% of it falling in the three wettest months (March is typically the wettest, July the driest).
How many extremely hot or cold days does Bostonia have?
On average, Bostonia sees about 0 day(s) a year at or above 40°C and about 0 day(s) at or below 0°C, based on 10 years of data.
Is Bostonia getting warmer?
Across the 10 years on file (2016–2025), the annual average temperature has moved by about -1.33°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 Bostonia?
The hottest day on file is 6 September 2020 at 38.2°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
- Bostonia — 32.750°, -117.000°, ERA5 grid cell center, 8.7 km from requested point
- Time zone
- America/Los_Angeles
- 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 (2026-07-18). Historical climate data for Bostonia, United States (32.75°N, 117.00°W), derived from ERA5 (Hersbach et al., 2023, Copernicus Climate Change Service). Retrieved from https://www.pastclimate.com/
PastClimate. (2026). Historical climate data for Bostonia, United States [Data set]. Derived from ERA5 (Copernicus Climate Change Service). Retrieved July 18, 2026, from https://www.pastclimate.com/
"Historical Climate Data for Bostonia, United States." PastClimate, derived from ERA5 (Copernicus Climate Change Service), July 18, 2026, www.pastclimate.com.
@misc{pastclimate,
author = {PastClimate},
title = {Historical climate data for Bostonia, United States},
year = {2026},
note = {Derived from ERA5 (Hersbach et al., 2023), Copernicus Climate Change Service. Accessed 2026-07-18},
url = {https://www.pastclimate.com/}
}Notice something wrong with this data? Report a data issue.