In Shizuoka the climate is temperate, with mild and sunny winters, and hot, humid and rainy summers. Like the rest of Japan, the city is affected by the monsoon circulation: in winter the northwest cold currents will prevail, while in summer they will be replaced by hot and humid currents of tropical origin.
Shizuoka is located in the central part of the island of Honshu, halfway between Nagoya and Tokyo, and on the coast, in Suruga Bay, an area particularly exposed to the summer monsoon. North of the city lie the Akaishi Mountains, or Southern Alps, with a series of peaks of around 3,000 metres (9,800 ft) and some winter resorts, while to the north-east lies Mount Fuji.
Given the relatively low latitude (we are on the 35th parallel), and the protection of the mountains (we are on the southern side), in winter the currents of Siberian origin are felt little, so there are several sunny days, and usually it's not very cold; however, cold and windy periods, with highs around 7/10 °C (45/50 °F) or less, can not be ruled out. Snowfall is very rare: unlike in Tokyo, where sometimes it can snow, here in practice it never snows. Night frosts are rare and usually light.
Although it rarely rains in winter, given the exposure to southern winds, when it rains, it can rain a lot.
In summer, sunny and muggy periods alternate with periods of bad weather, with wind and rain.
Here are the average temperatures.
Average temperatures - Shizuoka

Shizuoka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Shizuoka	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	2	2	6	10	15	19	23	24	21	15	9	4
Max (°C)	12	12	15	20	23	26	30	31	28	23	18	14
Min (°F)	36	36	43	50	59	66	73	75	70	59	48	39
Max (°F)	54	54	59	68	73	79	86	88	82	73	64	57

In Shizuoka precipitation is abundant: even 2,300 millimetres (90 inches) per year, so this it one of the rainiest cities in Japan (together with some cities in the northern side of the island of Honshu, such as Kanazawa and Komatsu). The driest season is definitely the winter; in summer, from June to September, more than 1,100 millimetres (43 inches) of rain fall.
Here is the average precipitation.
Average precipitation - Shizuoka

Shizuoka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Shizuoka	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	70	100	210	235	220	285	280	245	305	170	135	60	2320
Prec. (in)	2.8	3.9	8.3	9.3	8.7	11.2	11	9.6	12	6.7	5.3	2.4	91.3
Days	11	12	17	16	17	20	20	18	19	17	12	10	190

From June to October (but especially from August to early October), Shizuoka can be affected by typhoons, the tropical cyclones of the Pacific, which in this area, facing south, are felt in a particular way. The most intense typhoons can bring torrential rains and heavy damage.
The cherry blossoming in Shizuoka takes place around the 30th of March.
The amount of sunshine in Shizuoka is good in winter (there are almost 7 hours of sunshine per day in December and January), while it is just mediocre or decent in the other seasons, due to disturbances in spring and fall, and to the monsoon in summer. However, in summer August is the sunniest month.
Sunshine - Shizuoka

Shizuoka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Shizuoka	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	7	7	6	6	6	5	5	7	5	5	6	6

The sea is warm enough for swimming, with a temperature of 23 °C (73 °F) or more, from July to October, as you can see in the following table.
Sea temperature - Shizuoka

Shizuoka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Shizuoka	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	17	16	16	17	20	22	24	26	25	23	21	19
Sea (°F)	63	61	61	63	68	72	75	79	77	73	70	66