Summer in Sendai means warm days, steady humidity, and bursts of rain that really shape how you’ll experience the city. On average, daytime temperatures hover in the low 20s°C (mid-70s°F) up to about 30°C (86°F), so it’s comfortably warm without the oppressive extremes you might get in Tokyo or Osaka.
You’ll probably notice the air feels muggy at times, but that coastal breeze? It often keeps things more pleasant than you’d expect in other parts of Japan.
Early summer brings more rain thanks to the rainy season, but by July and August, you’ll see clearer skies along with higher heat and humidity. There’s still a lot of cloud cover, yet you get enough daylight for outdoor adventures.
Evenings cool off just enough, so wandering through lively streets or catching a festival feels pretty good.
Overview of Sendai’s Summer Climate
Sendai gets a warm but not sweltering summer, thanks to its spot on the coast and the monsoon. You’ll find moderate heat, plenty of humidity, and a steady mix of sun and clouds, with rain showing up often but not as dramatically as in southern Japan.
Climate Classification and General Characteristics
Sendai sits in a humid temperate climate zone. That means summers feel warm and wet, and winters turn cold with some snow.
Ocean air cools things off, so unlike Tokyo or Osaka, Sendai’s summer heat usually doesn’t get too intense.
Average highs in summer run from 26°C to 29°C (79°F to 84°F), and lows land around 18°C to 22°C (65°F to 72°F). The humidity makes the air feel warmer, especially in July and August.
Rain falls often between June and September, when you’ll see 145–195 mm of rain per month. The East Asian summer monsoon brings most of this wet weather.
Clouds hang around a lot, and sunshine hours drop compared to spring. You’ll spot more overcast days, but clear, hot stretches do happen. This balance keeps summer from feeling as harsh as it does in central Japan.
Summer Duration and Key Weather Patterns
Summer in Sendai usually runs from late June to early September. June kicks off the rainy season, and July and August bring the most heat and humidity.
September stays warm but gets wetter, with rainfall peaking for the year.
One odd thing about Sendai’s summer is the Yamase—a cool northeast wind. When it blows, temperatures dip, and even midsummer days can feel a bit chilly. This makes the weather less predictable and sometimes cooler than you’d expect.
Typhoons sometimes hit between August and early October, but they’re usually weaker than what southern Japan gets. You might deal with heavy rain and strong winds, but direct hits don’t happen that often.
The sea temperature tops out around 24–25°C in August, so late summer is actually the best time for swimming. Earlier in the season, the water might feel a little brisk.
Comparison to Other Seasons
Compared to winter, summer in Sendai is much milder—and a lot wetter. Winters bring highs near 5°C (41°F) and regular snow, while summer highs almost reach 30°C (86°F) with way more humidity.
In spring, you get more sun and less rain, especially in May, making it great for being outside. Summer, on the other hand, is cloudier and stickier, though it’s still more moderate than in many Japanese cities.
Autumn cools off quickly after September, with highs dropping into the teens by November. Rain backs off after the summer peak, so autumn feels drier and steadier.
Summer stands out as its own thing in Sendai, marked by warmth, humidity, and frequent rain, but the cool winds and brief extreme heat keep it from getting overwhelming.
Average Summer Temperatures in Sendai
Summer in Sendai feels warm, but not as hot as Tokyo or Osaka. You’ll get moderate highs, cooler nights, and humidity that builds as summer rolls on.
Temperatures rise from June into August, then drop a bit in September.
Typical Daytime and Nighttime Temperatures
Daytime highs in Sendai during summer go from 20°C (68°F) in early June to about 26°C (79°F) in August. The hottest afternoons usually land in early August, sometimes hitting 27°C (81°F).
Nights bring relief. Lows start near 14°C (57°F) in June and climb to around 20°C (68°F) in August. The most common midsummer low is about 22°C (72°F), which can feel muggy thanks to the humidity.
Sendai’s summer weather is milder than other big Japanese cities. Tokyo often breaks 30°C, but Sendai rarely does, so evenings are more comfortable for walks or outdoor dining.
Monthly Temperature Breakdown: June, July, August, September
- June: Highs hit about 22°C (72°F), lows near 15°C (59°F). Early summer feels cooler, but humidity starts to creep in.
- July: Highs climb to 25°C (77°F), lows close to 19°C (66°F). This is when it starts to get muggy.
- August: The hottest stretch, with highs near 26–27°C (79–81°F) and lows around 20–22°C (68–72°F). Nights can feel sticky.
- September: Temperatures ease off, with highs around 24°C (75°F) and lows near 18°C (64°F). The air dries out a bit.
This slow change makes summer in Sendai a bit easier to handle than in a lot of Japan.
Historical Temperature Extremes
Sendai’s averages stay pretty reasonable, but sometimes the city gets more extreme temperatures. On the hottest days, highs can reach 31°C (88°F), but that’s rare.
Nights almost never stay above 24°C (75°F), even in August.
Winter is a different story—temperatures drop below freezing, but that’s far from the summer vibe. The hottest day usually falls in early August, while the coldest is in late January.
So, overall, Sendai’s summer avoids extreme heat, offering more stable conditions for locals and visitors.
Rainfall and Humidity During Summer
Summer in Sendai means frequent rain, high humidity, and a real mix of sun and clouds. You’ll see wetter days than in spring, with July and September being especially rainy.
Humidity climbs fast, often making it feel hotter than the numbers suggest.
Rainy Season and Wettest Months
The rainy season, or tsuyu, kicks in around mid-June and lasts until mid-July. You’ll notice regular showers and steady rain during this stretch.
Rain stays high through August and really peaks in September, when typhoons occasionally swing by.
Sendai’s rainy season isn’t as wild as what you’d find farther south, but persistent dampness is common. Rain tends to alternate with short sunny breaks, making the weather a bit unpredictable if you’re planning outdoor stuff.
By late September, rain finally lets up, but the month still racks up the highest totals of the year. If you’re visiting then, pack for wet weather, especially in the afternoons when showers hit more often.
Average Monthly Rainfall
Sendai gets about 1275 mm of rain per year, with much of it falling in summer. June to September are the wettest, with July and September especially soggy.
| Month | Rainfall (mm) | Rainy Days |
|---|---|---|
| June | 145 | 12 |
| July | 180 | 16 |
| August | 160 | 13 |
| September | 195 | 13 |
You’ll see around 12–16 rainy days per month during summer. Showers can be quick but heavy, and sometimes you’ll get a whole day of steady rain.
Winter brings lighter, sleet or snow, but summer’s rain is heavier and more frequent.
Humidity Levels and Seasonal Variation
Humidity in Sendai skyrockets in summer, usually hitting 70–80% on a typical day. Warm temps and moist Pacific air make the season feel muggy, especially in July and August.
The Yamase wind sometimes cools things down, but it doesn’t really cut the humidity. Instead, it brings cloudy, damp air that makes everything feel even heavier.
Compared to spring and autumn, summer humidity is much higher. In May, it’s closer to 65–70%, but in peak summer it often tops 80%. If you don’t like humidity, you’ll feel the difference as soon as the rainy season starts.
Cloud Cover and Sunshine Hours
Summer in Sendai usually brings a mix of cloudy days and shorter bursts of sun. You’ll get a balance of overcast skies with moderate light, plus some clearer spells for outdoor plans.
Typical Cloudiness in Summer
Cloud cover sticks around a lot in Sendai during summer. Skies are overcast or mostly cloudy for more than half the season. About 59% of the time, you’ll be looking at clouds.
The rainy season, from late June into July, adds even more gray. Moist Pacific air fuels long stretches of gloomy weather. Heavy rain isn’t constant, but the cloud cover can make the whole season seem damp and a little dreary.
Sendai stays cooler and less humid than Tokyo or Osaka, but the clouds are still a big part of summer here. So, don’t expect tons of blue-sky days—light is often softer and more muted.
Some travelers find that the clouds actually help, taking the edge off the heat and making city walks more comfortable, even if the sun’s hiding.
Average Daily Sunshine Duration
In summer, sunshine hours in Sendai drop compared to spring and autumn. July gets about 4.1 hours of sun per day, while May and June see more—closer to 5–6 hours daily.
Clouds and rain both play a part in keeping sunshine hours low. Even in August, when rain backs off a bit, you rarely get as much sun as in April or October.
Daylight itself is long, with up to 14–15 hours from sunrise to sunset. Still, much of this time is filtered through clouds. You’ll have plenty of daylight for activities, but not always direct sun.
If you’re aiming for outdoor sightseeing, mornings are often your best bet for brighter skies. Afternoons usually see clouds build up, especially during the height of the rainy season.
Wind and Atmospheric Conditions
Summer in Sendai brings a mix of steady breezes and humid air patterns that shape how the season feels. You’ll notice cooler northeast winds and sometimes stretches of calm, muggy air that can impact comfort and visibility.
Air pressure stays pretty stable, but shifts can change up cloud cover and rain timing.
Prevailing Summer Winds
During summer, the Yamase wind blows in from the northeast, bringing cool, damp air from the Pacific. This wind drops daytime temperatures compared to inland cities and can make even midsummer days feel a bit chilly.
It also brings extra clouds and occasional drizzle, which cuts down on sunshine.
When the Yamase fades, warmer and stickier air moves in from the south. These winds can make things feel more like Tokyo’s summer, but that’s less common in Sendai.
Average wind speeds in summer stay pretty calm, around 4–5 mph, so strong gusts are rare. The direction of the wind matters more than the speed.
If you’re planning to be outdoors, expect breezy days that might feel cooler than the thermometer says, especially along the coast.
Air Pressure and Stability
Air pressure in Sendai during summer usually stays pretty steady, averaging close to 753 inHg. This means you won’t get as many sudden weather swings as you might in places with wild weather systems.
When the pressure drops a bit, it often hints that rain or cloudy weather is on the way.
Thanks to the humid subtropical climate, high pressure brings in warm, sticky air. That trapped moisture can make the air feel heavy, and sometimes it’s hard to see very far.
Lower pressure periods usually show up during the rainy season or when typhoons get close, though Sendai doesn’t get hit by typhoons as often as places farther south.
If you’re visiting, you’ll notice that these pressure patterns explain why one week can have both hot, sunny days and then a run of cooler, gray ones.
Travel Tips for Visiting Sendai in Summer
Summer in Sendai means warm days, high humidity, and all kinds of festivals. You’ll want to plan around the weather and whatever events are happening to really enjoy your trip.
Best Times to Visit
Late June to early July is usually the most comfortable stretch of summer, right after the rainy season starts letting up. Daytime highs are usually between 22–26°C (72–79°F), and you might even want a light jacket at night.
If you’re into lively crowds, early August is the peak. The Sendai Tanabata Festival runs from August 6–8, and the city gets covered in colorful streamers and decorations. On August 5, there’s a huge fireworks show near Jozenji-dori that draws a ton of people.
Just a heads-up, August is also the hottest month, with average highs around 28–30°C (82–86°F) and humidity that can feel relentless. Typhoons sometimes pass through, so it’s smart to check the weather if you’re traveling then.
If you’d rather avoid the crowds, late July is a good bet. You’ll get long daylight hours and warm weather, perfect for outdoor spots like Akiu Great Falls or a day exploring the coast.
What to Pack for the Weather
Get ready for both heat and sudden rain. I always reach for lightweight, breathable stuff—think cotton or linen—when it’s hot outside.
A short-sleeved shirt with light pants or shorts usually feels good during the day. Still, I’d toss a cardigan or thin hoodie in your bag for when you walk into those freezing air-conditioned places.
Rain showers can pop up, especially in June and July. I like carrying a compact umbrella or a light rain jacket, just in case.
If you hate soggy feet, go with waterproof shoes or quick-drying sneakers. Trust me, it makes a difference.
August brings that blazing sun, so don’t forget a wide-brimmed hat, sunglasses, and sunscreen. Sandals work if you’re just strolling, but honestly, sneakers are way better for sightseeing.
Planning to hit up a festival? Pack something casual and breathable. You’ll probably be outside for hours, surrounded by crowds, so comfort really matters.