Boulder
United States · 22 May 2018
Average
13.5°C
low 5°C · high 19.9°C
Rainfall
2.4mm
rain recorded
Wind
2.2m/s
daily average
Humidity
68.3%
daily average
Cloud
89%
cover
Pressure
1010hPa
daily average
The temperature ranged from 5°C around 04:00 to 19.9°C around 15:00. Rain was recorded across 4 hours, from around 14:00 to 18:00 (2.4mm total).
How unusual was this day?
Compared against the same 135 calendar days (±7 days) across the other 9 years on file.
High temperature
63th percentile
Low temperature
55th percentile
Rainfall
57th percentile
Wind
68th 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 10.9°C, versus 13.5°C on this specific day.
Sun & daylight
Sunrise
05:39
Sunset
20:15
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 | 10.5°C | 8.5°C | 0 | 1.5 | W | 74 | 1010 |
| 01:00 | 07:00 | 9.6°C | 7.4°C | 0 | 1.6 | W | 73 | 1011 |
| 02:00 | 08:00 | 9.3°C | 7°C | 0 | 1.6 | W | 74 | 1011 |
| 03:00 | 09:00 | 9°C | 6.6°C | 0 | 1.6 | W | 73 | 1010 |
| 04:00 | 10:00 | 5°C | 1.7°C | 0 | 2.7 | W | 91 | 1012 |
| 05:00 | 11:00 | 5.2°C | 2.1°C | 0 | 2.4 | W | 90 | 1012 |
| 06:00 | 12:00 | 5.3°C | 2.5°C | 0 | 2.1 | W | 89 | 1011 |
| 07:00 | 13:00 | 7.1°C | 4.5°C | 0 | 2.1 | W | 88 | 1012 |
| 08:00 | 14:00 | 11.9°C | 10.5°C | 0 | 1.4 | WSW | 77 | 1012 |
| 09:00 | 15:00 | 16.1°C | 14.4°C | 0 | 0.8 | W | 48 | 1012 |
| 10:00 | 16:00 | 16.8°C | 15.5°C | 0 | 0.4 | NW | 47 | 1011 |
| 11:00 | 17:00 | 18.8°C | 17.1°C | 0.01 | 1.1 | E | 44 | 1010 |
| 12:00 | 18:00 | 19.4°C | 17.1°C | 0.03 | 2.5 | E | 46 | 1009 |
| 13:00 | 19:00 | 19.3°C | 16.7°C | 0.02 | 3.3 | E | 49 | 1008 |
| 14:00 | 20:00 | 19.5°C | 17.4°C | 0.62 | 2.7 | ESE | 51 | 1008 |
| 15:00 | 21:00 | 19.9°C | 18.6°C | 0.04 | 1.7 | ENE | 51 | 1008 |
| 16:00 | 22:00 | 18.2°C | 16.2°C | 1.12 | 3 | NE | 58 | 1006 |
| 17:00 | 23:00 | 17.8°C | 15.9°C | 0.4 | 2.8 | NNW | 61 | 1007 |
| 18:00 | 00:00 | 17.9°C | 15.7°C | 0.16 | 3.1 | NW | 60 | 1008 |
| 19:00 | 01:00 | 18.3°C | 16°C | 0 | 3.2 | WNW | 58 | 1009 |
| 20:00 | 02:00 | 15.1°C | 12.9°C | 0 | 3.1 | WNW | 72 | 1010 |
| 21:00 | 03:00 | 12.7°C | 11°C | 0 | 2.7 | W | 87 | 1010 |
| 22:00 | 04:00 | 11.3°C | 9.2°C | 0 | 2.8 | W | 88 | 1011 |
| 23:00 | 05:00 | 10.4°C | 7.8°C | 0 | 3.2 | W | 88 | 1012 |
Nearby cities
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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 2018 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.