May weather forecast
San Francisco, Costa Rica

May exhibits a substantial escalation in the depth of the wet season in San Francisco. From April, temperatures slightly drop, and a remarkable amount of rainfall sets in. This month is characterized by the highest recorded rainfall of 339mm (13.35"), effectively saturating the city. Despite these conditions, the daylight hours peak, presenting captures of sunshine amidst the heavy showers. The cityscape's transformation in May is likely to be quite the spectacle for weather enthusiasts.

Temperature

The arrival of May in San Francisco denotes a barely perceptible change in the average high-temperatures to a still warm 27.7°C (81.9°F) from April's 29.7°C (85.5°F). Throughout the month of May, San Francisco observes an average nighttime temperature of 19.8°C (67.6°F).

Heat index

The average heat index in May is estimated at a hot 32°C (89.6°F). Long-standing exposure coupled with ongoing activity could result in exhaustion, possibly causing heat cramps.
Take into consideration that the heat index values are calculated for shade and light wind conditions. Exposure to unobstructed sunshine could lead to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'felt air temperature', is a single figure representing how weather conditions feel when combining temperature and humidity. Additional factors encompassing metabolic differences, the level of physical activity, and clothing can impact the individual's perception of temperature. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values remain especially vital for babies and toddlers. Young individuals are generally in more danger than adults due to their lower capacity to sweat. Moreover, their large skin surface in relation to their small bodies and the increased heat generation from their activities makes them more vulnerable.

Humidity

The average relative humidity in May is 82%.

Rainfall

In May, in San Francisco, the rain falls for 27.2 days. Throughout May, 339mm (13.35") of precipitation is accumulated. Throughout the year, in San Francisco, there are 272 rainfall days, and 2217mm (87.28") of precipitation is accumulated.

Daylight

The average length of the day in May in San Francisco is 12h and 35min.
On the first day of the month, sunrise is at 05:18 and sunset at 17:47. On the last day of May, sunrise is at 05:14 and sunset at 17:54 CST.

Sunshine

In San Francisco, the average sunshine in May is 7.8h.

UV index

The months with the lowest UV index in San Francisco are May, August and November, with an average maximum UV index of 5. A UV Index of 3 to 5 symbolizes a medium vulnerability from exposure to the Sun's UV rays for average individuals.
Note: The maximum daily UV index, 5 in May, converts into the following recommendations:
Take heed. Individuals of lighter complexion can be burned in less than half an hour. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. During bright days, sunglasses that offer UVA and UVB defense are recommended.