Map from Google - Sendai

In Sendai, a Japanese city in the north-east of Honshu Island, in Miyagi Prefecture, the climate is temperate humid, with cold winters, and warm 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 the hot and humid currents of tropical origin (although to a lesser extent than in central and southern Japan).
In winter, temperatures are low: in January and February, lows are slightly below freezing, and highs a few degrees above. Waves of intense cold are rare: usually the temperature does not drop below -5 °C, although the cold is fairly constant and the air humid. Even though the city is located on the east coast, snow is quite common, and sometimes abundant. An average of about 70 cm of snow per year fall, distributed in 66 days (in most cases, however, it is sleet or light snow).
In summer, the average temperatures are not too high, indeed during periods of bad weather there is a cool northeast wind called Yamase. However, in this season, periods of hot and humid weather, although rarer than in Tokyo, are possible, and alternate with periods of bad weather, with wind and rain.
Here are the average temperatures.
Average temperatures - Sendai
SendaiJanFebMarAprMayJunJulAugSepOctNovDec
SendaiJFMAMJJASOND
Min (°C)-2-21611162021181151
Max (°C)56915192226282419148

Precipitation is quite abundant, as it amounts to 1,250 millimetres per year; winter is the driest season (at least in quantity, as drizzle or sleet can often fall), while summer is the rainiest season.
Here is the average precipitation.
Average precipitation - Sendai
SendaiJanFebMarAprMayJunJulAugSepOctNovDecYear
SendaiJFMAMJJASONDY
Prec. (mm)35407010011014518016519012065351255
Days779101113161213987122

In late summer and early autumn, from August to October, Sendai may be affected by typhoons, but with less frequency and intensity than in southern Japan.
The cherry blossoming (Sakura) in Sendai occurs around April the 13th, about two or three weeks later than in Tokyo.
The amount of sunshine in Sendai is never very good: there are on average 4 and a half hours of sunshine per day in December and January, 6 hours in April and May, and only 4 hours in July and 4 ½ in August, due to the summer monsoon.

Sendai

The sea in Sendai, cold in winter, becomes acceptable for swimming in August and September, while in July it is still cool, as you can see in the table below.
Sea temperature - Sendai
SendaiJanFebMarAprMayJunJulAugSepOctNovDec
SendaiJFMAMJJASOND
Sea (°C)1188101317212423201713