December is one of the cooler months of the year in Casa Grande, with average highs near 19.1°C and lows around 5.1°C (mean 12.1°C). It is about average for rainfall, averaging 30 mm of rainfall and 48% relative humidity across the period.
December is one of the cooler months of the year in Casa Grande. Across 45 years of records, the warmest December in Casa Grande was 2025 — when the month averaged 16.6°C — while the coldest were 1987 and 2007 at 9.7°C. Typical December days reach 19.1°C with nights near 5.1°C. The long-term trend is warming, about 0.6°C per decade.
December is about average for rainfall in Casa Grande, averaging 30 mm of rainfall. The wettest December on record was 1984 with 101 mm, while the driest was 2024 at 0 mm.
Relative humidity in Casa Grande during December averages 48%. The most humid December was 1984 at 66%, and the least humid was 2005 at 27%.
December receives about 3.3 kWh/m²/day of solar energy in Casa Grande. The sunniest Decembers were 1985, 1999 and 2024 at 3.6 kWh/m²/day, and the cloudiest were 1984, 2008 and 2019 at 3.
Average wind speed in Casa Grande during December is 1.8 m/s. The windiest Decembers were 1982, 1988 and 1990 at 2.2 m/s, while the calmest were 2005, 2014 and 2022 at 1.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 11.6°C | 11.4°C | 11.6°C | 12.6°C | 14.3°C | +2.7°C |
| Avg High | 18.6°C | 18.6°C | 18.7°C | 19.2°C | 21.3°C | +2.7°C |
| Avg Low | 4.5°C | 4.3°C | 4.4°C | 5.9°C | 7.4°C | +2.9°C |
| Avg Rain | 37 mm | 35 mm | 20 mm | 29 mm | 29 mm | -8 mm |
December temperatures in Casa Grande have risen by about 2.8°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -6.6°C (1990) to a record high of 29.6°C (2021).
Rainfall in December is about average for rainfall, averaging 30 mm, with a wettest year of 101 mm.
A quieter season to visit Casa Grande
If your dates are flexible, the more temperate months of April and October tend to be the most comfortable for visiting Casa Grande. That said, December — with days averaging 19.1°C and nights around 5.1°C (mean 12.1°C) and low rainfall (30 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 🔥 | 23.7°C | 16.6°C | 9.4°C | 27.9°C | 4.0°C | 2 mm | 45% | 1.7 m/s | — |
| 2024 | 23.9°C | 16.1°C | 8.4°C | 28.3°C | 3.2°C | 0 mm | 28% | 1.6 m/s | 3.6 |
| 2023 | 21.3°C | 14.3°C | 7.3°C | 27.5°C | 2.2°C | 32 mm | 41% | 1.7 m/s | 3.3 |
| 2022 | 18.4°C | 12.3°C | 6.2°C | 23.9°C | -1.5°C | 68 mm | 57% | 1.5 m/s | 3.1 |
| 2021 | 20.8°C | 14.4°C | 8.0°C | 29.6°C | 0.4°C | 60 mm | 49% | 1.7 m/s | 3.1 |
| 2020 | 19.8°C | 12.3°C | 4.8°C | 26.2°C | 0.9°C | 9 mm | 32% | 1.9 m/s | 3.5 |
| 2019 | 17.9°C | 11.9°C | 5.9°C | 24.6°C | -1.6°C | 47 mm | 59% | 1.8 m/s | 3 |
| 2018 | 18.9°C | 12.4°C | 5.9°C | 24.5°C | -1.5°C | 21 mm | 48% | 1.6 m/s | 3.1 |
| 2017 | 22.4°C | 15.3°C | 8.2°C | 28.5°C | 1.6°C | 5 mm | 28% | 1.8 m/s | 3.2 |
| 2016 | 20.3°C | 14.0°C | 7.7°C | 27.0°C | 0.6°C | 40 mm | 50% | 1.8 m/s | 3.1 |
| 2015 | 17.9°C | 10.9°C | 3.9°C | 26.1°C | -0.7°C | 13 mm | 44% | 1.8 m/s | 3.3 |
| 2014 | 18.8°C | 13.0°C | 7.3°C | 25.4°C | -0.5°C | 40 mm | 53% | 1.5 m/s | 3.1 |
| 2013 | 18.7°C | 11.3°C | 3.8°C | 26.7°C | -2.3°C | 15 mm | 49% | 1.9 m/s | 3.4 |
| 2012 | 19.2°C | 12.7°C | 6.2°C | 27.8°C | -1.3°C | 37 mm | 45% | 1.7 m/s | 3.4 |
| 2011 | 16.7°C | 9.9°C | 3.2°C | 23.9°C | -2.4°C | 41 mm | 54% | 1.8 m/s | 3.1 |
| 2010 | 21.6°C | 14.5°C | 7.3°C | 28.0°C | -2.6°C | 35 mm | 43% | 1.9 m/s | 3.1 |
| 2009 | 17.2°C | 10.5°C | 3.8°C | 22.3°C | -1.3°C | 18 mm | 47% | 1.9 m/s | 3.2 |
| 2008 | 18.2°C | 11.6°C | 5.1°C | 26.1°C | -3.5°C | 44 mm | 54% | 2 m/s | 3 |
| 2007 | 16.4°C | 9.7°C | 3.0°C | 23.9°C | -2.4°C | 42 mm | 53% | 1.8 m/s | 3.4 |
| 2006 | 18.6°C | 11.3°C | 4.0°C | 25.7°C | -1.1°C | 6 mm | 39% | 1.9 m/s | 3.3 |
| 2005 | 21.0°C | 13.4°C | 5.8°C | 26.8°C | -1.0°C | 0 mm | 27% | 1.5 m/s | 3.4 |
| 2004 | 19.0°C | 11.7°C | 4.3°C | 26.1°C | -1.6°C | 39 mm | 51% | 2 m/s | 3.3 |
| 2003 | 19.9°C | 12.4°C | 4.9°C | 26.9°C | -3.3°C | 10 mm | 39% | 2.1 m/s | 3.5 |
| 2002 | 18.0°C | 11.4°C | 4.9°C | 23.1°C | -0.1°C | 15 mm | 51% | 1.7 m/s | 3.2 |
| 2001 | 17.8°C | 10.5°C | 3.2°C | 24.3°C | -1.5°C | 26 mm | 47% | 1.7 m/s | 3.3 |
| 2000 | 20.6°C | 13.0°C | 5.4°C | 24.4°C | 0.8°C | 1 mm | 46% | 1.8 m/s | 3.5 |
| 1999 | 20.1°C | 12.1°C | 4.2°C | 26.0°C | 0.1°C | 0 mm | 27% | 2 m/s | 3.6 |
| 1998 | 18.7°C | 11.1°C | 3.6°C | 25.7°C | -2.9°C | 10 mm | 48% | 1.9 m/s | 3.4 |
| 1997 | 16.7°C | 9.8°C | 2.9°C | 22.5°C | -3.2°C | 50 mm | 56% | 2 m/s | 3.4 |
| 1996 | 20.6°C | 12.9°C | 5.2°C | 27.8°C | -2.5°C | 1 mm | 39% | 1.9 m/s | 3.5 |
| 1995 | 20.8°C | 13.4°C | 6.1°C | 26.9°C | 1.8°C | 2 mm | 39% | 1.7 m/s | 3.4 |
| 1994 | 18.0°C | 11.5°C | 4.9°C | 24.1°C | -1.5°C | 80 mm | 59% | 1.9 m/s | 3.1 |
| 1993 | 18.8°C | 11.2°C | 3.5°C | 24.5°C | -1.8°C | 4 mm | 48% | 1.9 m/s | 3.5 |
| 1992 | 16.8°C | 10.2°C | 3.6°C | 21.6°C | -2.3°C | 96 mm | 62% | 1.8 m/s | 3.1 |
| 1991 | 18.3°C | 12.2°C | 6.0°C | 23.5°C | -1.5°C | 53 mm | 63% | 2 m/s | 3.1 |
| 1990 | 17.1°C | 9.9°C | 2.7°C | 25.0°C | -6.6°C | 53 mm | 52% | 2.2 m/s | 3.2 |
| 1989 | 20.1°C | 12.3°C | 4.6°C | 25.6°C | -1.6°C | 12 mm | 36% | 2 m/s | 3.5 |
| 1988 | 18.1°C | 11.0°C | 3.9°C | 24.5°C | -3.3°C | 5 mm | 46% | 2.2 m/s | 3.2 |
| 1987 ❄️ | 16.4°C | 9.7°C | 3.0°C | 24.7°C | -4.1°C | 39 mm | 53% | 1.8 m/s | 3.1 |
| 1986 | 18.2°C | 11.3°C | 4.4°C | 24.3°C | -0.5°C | 50 mm | 57% | 1.7 m/s | 3.1 |
| 1985 | 19.4°C | 11.8°C | 4.1°C | 23.7°C | -2.3°C | 23 mm | 53% | 1.8 m/s | 3.6 |
| 1984 🌧️ | 17.5°C | 11.6°C | 5.8°C | 24.7°C | 0.1°C | 101 mm | 66% | 2.1 m/s | 3 |
| 1983 | 18.6°C | 12.0°C | 5.3°C | 23.7°C | -1.3°C | 50 mm | 63% | 2 m/s | — |
| 1982 | 17.3°C | 10.6°C | 3.9°C | 23.3°C | -0.7°C | 53 mm | 59% | 2.2 m/s | — |
| 1981 | 21.4°C | 13.7°C | 5.9°C | 28.0°C | -2.3°C | 2 mm | 45% | 1.7 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 19.1°C with lows near 5.1°C (mean 12.1°C), based on 45 years of NASA POWER data.
December averages 30 mm of rainfall in Casa Grande, about average for rainfall. The wettest on record was 101 mm in 1984.
The hottest December reached 29.6°C in 2021. The coldest dipped to -6.6°C in 1990.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 2.8°C. Daytime highs moved from 18.8°C to 21.6°C and overnight lows from 5°C to 7.9°C over the same span.
December is one of the cooler months of the year in Casa Grande and about average for rainfall, so plan for around 19.1°C daytime highs and 5.1°C at night.
Not quite — December is the 2nd coolest month in Casa Grande, averaging 12.1°C.
For December in Casa Grande, pack warm layers and a jacket for chilly mornings, with typical highs of 19.1°C and lows of 5.1°C.
Relative humidity in December averages 48% — relatively dry.
Average wind speed in December is 1.8 m/s. The windiest December on record averaged 2.2 m/s (1982).
The wettest December on record was 1984 with 101 mm. On average, December sees 30 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Casa Grande behaves each December, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for December specifically, along with year-by-year records and how the month has changed over the decades.
