Home / Altadena / 21 December 2016
Altadena
United States · 21 December 2016
← 20 December 201622 December 2016 →
Average
12.2°C
low 9.2°C · high 17.3°C
Rainfall
6.8mm
rain recorded
Wind
3.1m/s
daily average
Humidity
41.8%
daily average
Cloud
72%
cover
Pressure
1017hPa
daily average
The temperature ranged from 9.2°C around 03:00 to 17.3°C around 11:00. Rain was recorded across 12 hours, from around 11:00 to 23:00 (6.9mm total).
How unusual was this day?
Compared against the same 135 calendar days (±7 days) across the other 9 years on file.
High temperature
48th percentile
Low temperature
73th percentile
Rainfall
88th percentile
Wind
96th 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 11.7°C, versus 12.2°C on this specific day.
Sun & daylight
Sunrise
06:55
Sunset
16:47
Day length
9h 52m
Hour by hour
Temperature (line) and hourly rainfall (bars), local time — America/Los_Angeles.
Cumulative rainfall through the day.
| Local time | UTC | Temp | Feels | Rain mm | Wind m/s | Dir | Humidity % | Pressure hPa |
|---|---|---|---|---|---|---|---|---|
| 00:00 | 08:00 | 11.7°C | 7.2°C | 0 | 2.8 | NNE | 33 | 1020 |
| 01:00 | 09:00 | 10.5°C | 6.2°C | 0 | 2.7 | NNE | 38 | 1019 |
| 02:00 | 10:00 | 10.6°C | 6.3°C | 0 | 2.5 | NNE | 33 | 1019 |
| 03:00 | 11:00 | 9.2°C | 4.5°C | 0 | 2.9 | NNE | 35 | 1019 |
| 04:00 | 12:00 | 10.1°C | 5.4°C | 0 | 3.1 | NNE | 36 | 1019 |
| 05:00 | 13:00 | 10.4°C | 5.5°C | 0 | 3.5 | NNE | 38 | 1018 |
| 06:00 | 14:00 | 10.3°C | 5.6°C | 0 | 3.3 | NNE | 39 | 1018 |
| 07:00 | 15:00 | 10.8°C | 6.1°C | 0 | 3.3 | NNE | 37 | 1018 |
| 08:00 | 16:00 | 12°C | 6.9°C | 0 | 3.5 | NNE | 28 | 1018 |
| 09:00 | 17:00 | 14.3°C | 9.1°C | 0 | 3.2 | NNE | 20 | 1018 |
| 10:00 | 18:00 | 16.7°C | 11.4°C | 0 | 3 | NNE | 14 | 1018 |
| 11:00 | 19:00 | 17.3°C | 12.3°C | 0.1 | 2.8 | NE | 13 | 1018 |
| 12:00 | 20:00 | 17.3°C | 12.3°C | 0 | 2.7 | NE | 14 | 1017 |
| 13:00 | 21:00 | 16.7°C | 11.9°C | 0.58 | 2.9 | NE | 20 | 1017 |
| 14:00 | 22:00 | 13.5°C | 9.5°C | 0.65 | 2.7 | NNE | 37 | 1017 |
| 15:00 | 23:00 | 12.7°C | 9.3°C | 0.65 | 2.2 | NNE | 44 | 1016 |
| 16:00 | 00:00 | 11.8°C | 8.5°C | 0.11 | 2.6 | NNE | 54 | 1016 |
| 17:00 | 01:00 | 11.6°C | 8.1°C | 0.34 | 3 | NNE | 58 | 1015 |
| 18:00 | 02:00 | 11.6°C | 8°C | 0.22 | 3.3 | NNE | 59 | 1015 |
| 19:00 | 03:00 | 11.4°C | 8.1°C | 0.43 | 3.3 | NNE | 69 | 1015 |
| 20:00 | 04:00 | 11.3°C | 8.3°C | 0.32 | 3 | NNE | 71 | 1015 |
| 21:00 | 05:00 | 10.9°C | 7.5°C | 0.12 | 3.3 | NE | 69 | 1016 |
| 22:00 | 06:00 | 10.5°C | 6.9°C | 0.18 | 3.7 | NNE | 72 | 1016 |
| 23:00 | 07:00 | 9.8°C | 5.8°C | 3.17 | 4 | NNE | 70 | 1016 |
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
- Altadena — 34.250°, -118.250°, ERA5 grid cell center, 12.8 km from requested point
- Time zone
- America/Los_Angeles
- What's shown here
- The hourly and daily record for 21 December 2016 specifically — not a monthly average. See the Altadena 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 Altadena, United States (34.25°N, 118.25°W), derived from ERA5 (Hersbach et al., 2023, Copernicus Climate Change Service). Retrieved from https://www.pastclimate.com/
PastClimate. (2026). Historical climate data for Altadena, United States [Data set]. Derived from ERA5 (Copernicus Climate Change Service). Retrieved July 20, 2026, from https://www.pastclimate.com/
"Historical Climate Data for Altadena, 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 Altadena, 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.