December weather forecast
San Francisco, Argentina

The first month of the summer, December, is a hot month in San Francisco, Argentina, with temperature in the range of an average high of 32.5°C (90.5°F) and an average low of 18.5°C (65.3°F).

Temperature

December's advent notes a subtle adjustment in average high-temperature to a hot 32.5°C (90.5°F) from November. San Francisco logs a considerable temperature decrease from the daytime highs during the nights in December, with an average reading of 18.5°C (65.3°F).

Heat index

The average heat index in December is estimated at a sweltering 36°C (96.8°F). Undertake extra safety actions, heat cramps and heat exhaustion are expected. Heatstroke may result from lengthy activity.
It is emphasized that the heat index's values are meant for shaded zones with mild winds. Direct sunlight can cause a surge in the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', is derived by integrating air temperature with the existing relative humidity to express the perceived warmth. Additional factors encompassing metabolic differences, the level of physical activity, and clothing can impact the individual's perception of temperature. Direct exposure to sun rays can potentially augment the heat sensation, elevating the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly relevant to babies and toddlers. Young ones are generally more prone to risk than adults due to their reduced ability to sweat. Their large skin surface area relative to their diminutive bodies and elevated heat production from their activities further enhance this risk.
As a reaction to high temperatures, the human body begins to perspire, using the evaporation of sweat to lower its temperature. Increased relative humidity interferes with body cooling by slowing the rate of evaporation, resulting in a slower body cooling rate and a heightened feeling of heat. When heat gain surpasses the level the body can shed, body temperature begins to increase, and consequently, overheating and dehydration can occur, with varying severity.

Humidity

The average relative humidity in December is 51%.

Rainfall

In San Francisco, in December, it is raining for 9.5 days, with typically 55mm (2.17") of accumulated precipitation. Throughout the year, there are 91.8 rainfall days, and 449mm (17.68") of precipitation is accumulated.

Daylight

December has the longest days of the year, with an average of 14h and 12min of daylight.
On the first day of the month, sunrise is at 05:56 and sunset at 19:59. On the last day of December, in San Francisco, sunrise is at 06:06 and sunset at 20:16 -03.

Sunshine

With an average of 10.4h of sunshine, December has the most sunshine of the year.

UV index

The months with the highest UV index are January, February and December, with an average maximum UV index of 7. A UV Index of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV radiation for the ordinary person.
Note: The UV index of 7 in December translates into these instructions:
Inhibit overexposure. Warding off sun damage is of utmost importance. Between 10 a.m. and 4 p.m., the Sun's UV radiation is at its peak. Limit your exposure to direct sunlight during these hours. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes.