Boulder
United States · 22 May 2021
Average
10.5°C
low 4°C · high 15.4°C
Rainfall
4.3mm
rain recorded
Wind
2.1m/s
daily average
Humidity
78.4%
daily average
Cloud
65%
cover
Pressure
1016hPa
daily average
The temperature ranged from 4°C around 03:00 to 15.4°C around 15:00. Rain was recorded across 8 hours, from around 12:00 to 19:00 (4.3mm total).
How unusual was this day?
Compared against the same 135 calendar days (±7 days) across the other 9 years on file.
High temperature
31th percentile
Low temperature
42th percentile
Rainfall
67th percentile
Wind
61th percentile
A percentile of 100 means this was the hottest/wettest/windiest of the comparable days on file; 50 is right in the middle. This window's average temperature was 11°C, versus 10.5°C on this specific day.
Sun & daylight
Sunrise
05:39
Sunset
20:16
Day length
14h 36m
Hour by hour
Temperature (line) and hourly rainfall (bars), local time — America/Denver.
Cumulative rainfall through the day.
| Local time | UTC | Temp | Feels | Rain mm | Wind m/s | Dir | Humidity % | Pressure hPa |
|---|---|---|---|---|---|---|---|---|
| 00:00 | 06:00 | 9.5°C | 7.1°C | 0 | 1.3 | W | 65 | 1012 |
| 01:00 | 07:00 | 8°C | 5.6°C | 0 | 1.2 | W | 71 | 1013 |
| 02:00 | 08:00 | 6°C | 3.5°C | 0 | 1.4 | W | 82 | 1013 |
| 03:00 | 09:00 | 4°C | 1.2°C | 0 | 1.8 | W | 88 | 1015 |
| 04:00 | 10:00 | 5.6°C | 2.7°C | 0 | 2.5 | WNW | 91 | 1016 |
| 05:00 | 11:00 | 5.7°C | 3.2°C | 0 | 1.9 | WNW | 93 | 1017 |
| 06:00 | 12:00 | 5.9°C | 3.5°C | 0 | 1.7 | W | 92 | 1017 |
| 07:00 | 13:00 | 7.6°C | 5.4°C | 0 | 1.8 | WNW | 88 | 1018 |
| 08:00 | 14:00 | 10.2°C | 9.2°C | 0 | 0.5 | N | 81 | 1018 |
| 09:00 | 15:00 | 12°C | 10.3°C | 0 | 1.6 | E | 74 | 1018 |
| 10:00 | 16:00 | 13°C | 10.5°C | 0.02 | 2.6 | E | 69 | 1018 |
| 11:00 | 17:00 | 13.7°C | 11°C | 0 | 3.2 | E | 68 | 1018 |
| 12:00 | 18:00 | 13.6°C | 11°C | 0.27 | 3.1 | ENE | 69 | 1018 |
| 13:00 | 19:00 | 14.9°C | 12.6°C | 0.31 | 2.9 | E | 68 | 1018 |
| 14:00 | 20:00 | 15°C | 12.6°C | 0.34 | 3.3 | E | 69 | 1017 |
| 15:00 | 21:00 | 15.4°C | 13.3°C | 0.89 | 2.7 | ENE | 67 | 1017 |
| 16:00 | 22:00 | 11.9°C | 9.9°C | 0.89 | 2.7 | ENE | 86 | 1015 |
| 17:00 | 23:00 | 12.9°C | 10.3°C | 0.55 | 3.6 | ENE | 79 | 1015 |
| 18:00 | 00:00 | 13°C | 10.8°C | 0.69 | 2.6 | ENE | 75 | 1016 |
| 19:00 | 01:00 | 12.5°C | 11.1°C | 0.32 | 1.6 | NE | 79 | 1015 |
| 20:00 | 02:00 | 11.4°C | 10.2°C | 0.01 | 1.3 | NE | 83 | 1016 |
| 21:00 | 03:00 | 10.4°C | 8.9°C | 0.01 | 1.3 | NE | 81 | 1016 |
| 22:00 | 04:00 | 10°C | 8.1°C | 0 | 1.8 | NE | 83 | 1016 |
| 23:00 | 05:00 | 10.2°C | 8.3°C | 0 | 1.7 | NE | 81 | 1015 |
Nearby cities
Need this verified for an official or legal purpose? Request a weather verification report.
Data 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
- Boulder — 40.000°, -105.250°, ERA5 grid cell center, 2.4 km from requested point
- Time zone
- America/Denver
- What's shown here
- The hourly and daily record for 22 May 2021 specifically — not a monthly average. See the Boulder climate overview for typical conditions.
- 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 Boulder, United States (40.00°N, 105.25°W), derived from ERA5 (Hersbach et al., 2023, Copernicus Climate Change Service). Retrieved from https://www.pastclimate.com/
PastClimate. (2026). Historical climate data for Boulder, United States [Data set]. Derived from ERA5 (Copernicus Climate Change Service). Retrieved July 20, 2026, from https://www.pastclimate.com/
"Historical Climate Data for Boulder, 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 Boulder, 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.