Climate and monthly weather forecastSanta Rosa, CA

The climate of Santa Rosa

Nestled in the heart of the state's wine country, Santa Rosa experiences a warm Mediterranean climate classified as Csb according to the Köppen climate classification system. By parsing these conditions carefully, a pattern emerges across its annual weather cycles.

Temperature highs in Santa Rosa range from a mild 57.2°F (14°C) in the height of winter to a pleasant 79.7°F (26.5°C) in the peak of the summer season, revealing a moderate weather pattern throughout the year. The coldest monthly low falls to 41.9°F (5.5°C) during the wintertime while the warmest monthly low sits at 54.7°F (12.6°C) during the hottest peak periods in summer. These temperatures denote a moderate climate, devoid of extreme temperature fluctuations.

Santa Rosa's rainfall averages balance between 0.04" (1mm) during the lean season in July and August, spiking up to 2.64" (67mm) in February. The number of rainfall days, likewise, varies from 0.8 days in August and increases to 12.6 days in March. This suggests that the seasonality of rainfall aligns largely with the turn of the year into spring.

Another key parameter in Santa Rosa’s climate is sunshine. At its peak in July, residents enjoy up to an average of 14.5 daylight hours and 11.9 hours of sunshine, highlighting Santa Rosa's typically sunny summers. The shortest daylight period is experienced in December with 9.5 hours, leading to 5.7 hours of sunshine, delineating a noticeable but not drastic reduction in the winter months. Unsurprisingly, alongside this, the highest UV index is observed in June at a reading of 6, decreasing to as low as 3 in winter months.

The locality exhibits 36% cloud cover in January while the least cloud cover is reported in July, with only 9%. Correspondingly, wind speeds vary but not dramatically, with the fastest recorded winds appearing in May at 7.1mph (11.4km/h). Wind gusts mirror this pattern, peaking at 10.9mph (17.5km/h) in April and tapering down to 7.7mph (12.4km/h) in August.

The best time to visit Santa Rosa

Considering the variety of weather parameters, the best time to visit Santa Rosa would arguably be from end of Spring to early Fall, between May and October. The charm of this period lies in the long daylight hours and abundant sunshine, which peak between June and August. Minimal rainfall, along with moderate temperatures averaging between 64.9°F (18.3°C) and 79.3°F (26.3°C) during day and from 45.5°F (7.5°C) to 54.7°F (12.6°C) at night, provide the perfect conditions for exploring the wineries and nature reserves in the region.

The worst time to visit Santa Rosa

Visitors looking to avoid the less favourable weather conditions in Santa Rosa should steer clear of late winter to early spring. Between February and March, the city experiences the highest rainfall, with up to 12.6 days of rain and an average of 2.64" (67mm) falling in February. While the temperatures during this time are not particularly extreme, ranging on average from 42.8°F (6°C) to 60.4°F (15.8°C), the wet conditions could be uncomfortable for outdoor activities.

Spring weather in Santa Rosa

As March rolls into April and May, Spring announces its arrival in Santa Rosa with an appreciable decline in rainfall. The city experiences over 13.2 daylight hours by April, giving residents and visitors more time to soak up the abundant sunshine, which exceeds 10 hours per day. Average highs during this time start from 60.4°F (15.8°C) in March and climb to 69.1°F (20.6°C) by May, while lows gradually increase from 43.5°F (6.4°C) to 48.6°F (9.2°C).

Summer weather in Santa Rosa

Summers in Santa Rosa are largely dry and sunny, with the least rainfall recorded and only an average of 1.5 to 1.9 days of rain, from June to August. Day temperatures rise to highs between 76.3°F (24.6°C) and 79.7°F (26.5°C), while nighttime temperatures range comfortably from 53.1°F (11.7°C) to 54.7°F (12.6°C). These months see more than 14 daylight hours per day, and Santa Rosa basks under almost 12 hours of daily sunshine.

Autumn weather in Santa Rosa

The Autumn season in Santa Rosa, spanning September to November, is characterized by a gradual cooling of temperatures, with average highs decreasing from 79°F (26.1°C) to 63.1°F (17.3°C), and lows reducing from 54.7°F (12.6°C) down to 46°F (7.8°C). Rainfall begins to show a slight increase going from 0.12" (3mm) in September to 1.02" (26mm) in November. Sunshine hours per day and daylight hours slowly start to decrease to prepare for winter.

Winter weather in Santa Rosa

Winter in Santa Rosa does not see severe chilling temperatures as some might expect. In fact, December's temperatures range from 41.9°F (5.5°C) during the coolest nights to 55.6°F (13.1°C) at daytime's peak. Rainfall significantly increases during this season, receiving about over 2" (51mm) in December and peaking in February at 2.64" (67mm). With daylight and sunshine hours reducing to their annual lows, the overall wintertime climate might feel colder due to the combined effect of increased humidity, higher cloud cover, and prevailing winds.

Weather in January

In Santa Rosa, California, January kicks off with lower temperatures than the preceding December. The climate in January tends to favor more humidity and a significant amount of rainfall, with the rain gauge reading an average of 2.01" (51mm) during this month. Weather in January »

Weather in February

Transitioning from January to February, Santa Rosa sees a slight uptick in temperatures, though the weather remains within the realm of winter characteristics. February experiences marginally lower rainfall and fewer rainy days than January, but relative humidity remains constant. Weather in February »

Weather in March

March signifies a subtle shift towards spring in Santa Rosa, California. The highest rainfall can be observed during March, a total of 2.01" (51mm), interspersed over 12.6 days. Despite the increase in rain, temperature trends align with the approach of spring, exhibiting a subtle rise from the February readings. Weather in March »

Weather in April

In comparison to March, April displays obvious signs of spring. A perceptible decrease in rainfall coupled with an increase in daylight hours sets the stage for the warmer months ahead in Santa Rosa. The increase in temperature is accompanied by a general decrease in humidity. Weather in April »

Weather in May

In Santa Rosa, May ushers in the warmer temperatures associated with late spring and early summer. The notable decrease in rainfall, down to 0.55" (14mm), is indicative of the drier season ahead. Also, the rise in temperature reflects the changing seasons in a subtle, climatic transition. Weather in May »

Weather in June

June in Santa Rosa is generally marked by warmer weather, leaning towards typical summer conditions. Interestingly, June witnesses the longest daylight hours at 14.8, offering ample time for outdoor activities. The rise in UV index suggests stronger sunlight, indicating the need for sun protection. Weather in June »

Weather in July

July in Santa Rosa, stepping into the depth of summer, records the highest temperatures, reaching up to 79.3°F (26.3°C). This hot month showcases declining rainfall and less cloud cover compared to the preceding June, thereby cementing the grip of the summer season. Weather in July »

Weather in August

As the final month of summer, August in Santa Rosa is marked by warm temperatures comparable to July. The almost negligible rainfall of 0.04" (1mm) further emphasizes the arid conditions. Furthermore, the fewest cloudy days in the year are noticed during August, emphasizing clear skies and plenty of sunshine. Weather in August »

Weather in September

In Santa Rosa, September transitions from summer to fall with temperatures cooling down moderately from August. The slight increase in rainfall compared to the bone-dry summer months also nudges the weather towards fall. The steady decrease in daylight hours continues through September, indicating the passage of seasons. Weather in September »

Weather in October

October captures the essence of fall in Santa Rosa with significantly cooler conditions compared to September. A continuous trend of increasing rainfall and decreasing daylight hours signals the deepening fall season. Following the weather pattern, the temperature keeps dropping, preparing the environment for the incoming winter. Weather in October »

Weather in November

November in Santa Rosa experiences further drops in temperature and daylight hours, leading the transition from fall into early winter. With the highest post-summer rainfall of 1.02" (26mm), November underscores the shift towards the cold season. Weather in November »

Weather in December

Closing out the year, December in Santa Rosa epitomizes the winter season in the city. Though temperatures and daylight hours fall noticeably from November levels, the winter here is relatively mild and temperate. Correspondingly, the increase in rainfall from 1.02" (26mm) to 2.24" (57mm) in December highlights the winter imprint. Weather in December »