Home / Altadena / 23 December 2018
Altadena
United States · 23 December 2018
← 22 December 201824 December 2018 →
Average
13°C
low 7.4°C · high 19.2°C
Rainfall
0mm
dry day
Wind
1.6m/s
daily average
Humidity
48.3%
daily average
Cloud
74%
cover
Pressure
1019hPa
daily average
The temperature ranged from 7.4°C around 04:00 to 19.2°C around 14:00. No measurable rain was recorded during the day.
How unusual was this day?
Compared against the same 135 calendar days (±7 days) across the other 9 years on file.
High temperature
68th percentile
Low temperature
56th percentile
Rainfall
66th percentile
Wind
28th 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 11.4°C, versus 13°C on this specific day.
Sun & daylight
Sunrise
06:56
Sunset
16:48
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 | 10.5°C | 7.3°C | 0 | 2.2 | NNE | 54 | 1019 |
| 01:00 | 09:00 | 10°C | 6.9°C | 0 | 1.9 | NNE | 55 | 1019 |
| 02:00 | 10:00 | 9.1°C | 5.7°C | 0 | 2.3 | NNE | 56 | 1020 |
| 03:00 | 11:00 | 8.3°C | 4.8°C | 0 | 2.2 | NNE | 59 | 1020 |
| 04:00 | 12:00 | 7.4°C | 4.1°C | 0 | 2 | NNE | 60 | 1019 |
| 05:00 | 13:00 | 7.7°C | 4.3°C | 0 | 2.1 | NNE | 59 | 1019 |
| 06:00 | 14:00 | 8.1°C | 4.7°C | 0 | 2.1 | NE | 59 | 1020 |
| 07:00 | 15:00 | 8.1°C | 4.7°C | 0 | 1.9 | NNE | 55 | 1020 |
| 08:00 | 16:00 | 9.5°C | 6°C | 0 | 2.1 | NNE | 51 | 1020 |
| 09:00 | 17:00 | 12.5°C | 9.2°C | 0 | 1.8 | NNE | 42 | 1021 |
| 10:00 | 18:00 | 14.7°C | 12.3°C | 0 | 0.6 | NE | 36 | 1021 |
| 11:00 | 19:00 | 16.7°C | 14.5°C | 0 | 0.3 | W | 33 | 1021 |
| 12:00 | 20:00 | 17.7°C | 15.5°C | 0 | 0.6 | SW | 32 | 1020 |
| 13:00 | 21:00 | 19°C | 16.3°C | 0 | 1.1 | SW | 29 | 1019 |
| 14:00 | 22:00 | 19.2°C | 16.4°C | 0 | 1.2 | SW | 29 | 1018 |
| 15:00 | 23:00 | 18.8°C | 16.1°C | 0 | 1.3 | SW | 31 | 1018 |
| 16:00 | 00:00 | 17.8°C | 15.8°C | 0 | 1 | SW | 40 | 1019 |
| 17:00 | 01:00 | 16.9°C | 15°C | 0 | 1.3 | WSW | 46 | 1019 |
| 18:00 | 02:00 | 16.4°C | 14.2°C | 0 | 1.5 | NNW | 46 | 1019 |
| 19:00 | 03:00 | 14.6°C | 12.5°C | 0 | 1.6 | NNE | 57 | 1019 |
| 20:00 | 04:00 | 12.7°C | 10.7°C | 0 | 1.6 | NNE | 64 | 1019 |
| 21:00 | 05:00 | 12.7°C | 10.5°C | 0 | 1.2 | NNE | 57 | 1019 |
| 22:00 | 06:00 | 12.2°C | 9.6°C | 0 | 1.6 | NNE | 54 | 1019 |
| 23:00 | 07:00 | 11.8°C | 8.9°C | 0 | 1.9 | NNE | 54 | 1020 |
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 23 December 2018 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 (2026-07-19). 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 19, 2026, from https://www.pastclimate.com/
"Historical Climate Data for Altadena, United States." PastClimate, derived from ERA5 (Copernicus Climate Change Service), July 19, 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 2026-07-19},
url = {https://www.pastclimate.com/}
}Notice something wrong with this data? Report a data issue.