Hokkaido · Japan · 43.93° N · 141.64° E
Solar position in Rumoi
Sun position, daylight and the best solar panel angle for Rumoi — computed for 43.93° N, 141.64° E, 35 m above sea level.
The sun right now
Sun in Rumoi today
Sunday, 25 October 2026 · local time UTC+9
| Event | Time | Direction / height |
|---|---|---|
| Astronomical dawn | 04:23 | sun 18° below horizon |
| Nautical dawn | 04:56 | 12° below |
| Civil dawn | 05:30 | 6° below |
| Sunrise | 05:59 | 106° ESE |
| Golden hour ends | 06:40 | sun 6° up |
| Solar noon | 11:17 | 34.0° high |
| Golden hour starts | 15:54 | sun 6° up |
| Sunset | 16:34 | 254° WSW |
| Civil dusk | 17:04 | 6° below |
| Nautical dusk | 17:37 | 12° below |
| Astronomical dusk | 18:11 | 18° below |
| Day length | 10 h 35 min | |
Sun path diagram for Rumoi
Where the sun stands in the sky: the centre is straight overhead, the outer ring is the horizon. Numbers mark local clock hours.
- June solstice
- Equinox
- December solstice
- Today
On the June solstice the sun reaches 69.5° at solar noon in Rumoi; on the December solstice only 22.7°. Sunrise swings from 56° NE in June to 123° ESE in December — a 67° arc along the horizon.
Sunrise, sunset and sun height by month
Values for the 21st of each month, local clock time including daylight saving time.
| Month | Sunrise | Solar noon | Sunset | Day length | Noon elevation |
|---|---|---|---|---|---|
| January | 07:01 | 11:44 | 16:28 | 9 h 27 min | 26.2° |
| February | 06:24 | 11:47 | 17:10 | 10 h 46 min | 35.5° |
| March | 05:35 | 11:40 | 17:46 | 12 h 11 min | 46.3° |
| April | 04:41 | 11:32 | 18:23 | 13 h 43 min | 57.9° |
| May | 04:02 | 11:30 | 18:58 | 14 h 56 min | 66.2° |
| June | 03:50 | 11:35 | 19:19 | 15 h 29 min | 69.5° |
| July | 04:09 | 11:39 | 19:09 | 14 h 59 min | 66.6° |
| August | 04:43 | 11:36 | 18:28 | 13 h 45 min | 58.2° |
| September | 05:18 | 11:26 | 17:33 | 12 h 15 min | 46.8° |
| October | 05:54 | 11:17 | 16:40 | 10 h 46 min | 35.4° |
| November | 06:35 | 11:19 | 16:02 | 9 h 27 min | 26.2° |
| December | 07:04 | 11:31 | 15:58 | 8 h 54 min | 22.7° |
A year of daylight in Rumoi
Each column is one day of 2026. Bright: sun above the horizon; soft: civil twilight; line: solar noon. Steps are daylight saving time changes.
Best solar panel angle in Rumoi
Fixed array facing south (azimuth 180°). Energy per kWp from NASA POWER monthly climate, including clouds, temperature and snow reflection.
34°collects the most energy over a year: 1132 kWh per kWp.
71°gives the most in the darkest month — the one an off-grid system is sized for.
- Yearly energy
- Worst-month energy
| Tilt | kWh/kWp per year | Share of best year | December kWh/kWp/day | Best ÷ worst month |
|---|---|---|---|---|
| 0° | 982 | 87% | 0.76 | 5.7× |
| 15° | 1084 | 96% | 1.03 | 4.4× |
| 30° | 1130 | 100% | 1.25 | 3.5× |
| 34° year-round best | 1132 | 100% | 1.30 | 3.3× |
| 44° = latitude | 1119 | 99% | 1.41 | 3.0× |
| 45° | 1116 | 99% | 1.42 | 2.9× |
| 60° | 1045 | 92% | 1.51 | 2.5× |
| 70° | 968 | 86% | 1.53 | 2.2× |
| 71° off-grid best | 959 | 85% | 1.53 | 2.2× |
| 90° | 756 | 67% | 1.47 | 1.9× |
A fixed array in Rumoi produces the most over a year at 34°. The design month for an off-grid system is December: at 71° it makes 1.53 kWh per kWp a day, 18% more than at 34°, and costs 15% of the yearly total. Why steep panels win winter.
Off-grid solar in Rumoi at 70°
Daily energy of 1 kWp by month. Bars: panels at 70°. Line: panels at 34° (year-round best).
| Month | Sun hours, flat | Sun hours at 70° | kWh/kWp/day at 70° | at 34° | Mean temp. |
|---|---|---|---|---|---|
| January snow | 1.20 | 2.08 | 1.90 | 1.63 | -5.1 °C |
| February snow | 1.94 | 2.79 | 2.55 | 2.37 | -5.0 °C |
| March snow | 3.14 | 3.55 | 3.21 | 3.39 | -1.5 °C |
| April | 4.51 | 3.86 | 3.42 | 4.26 | 4.1 °C |
| May | 5.15 | 3.62 | 3.12 | 4.36 | 9.9 °C |
| June | 5.11 | 3.28 | 2.76 | 4.06 | 14.7 °C |
| July | 4.81 | 3.22 | 2.67 | 3.83 | 18.7 °C |
| August | 4.43 | 3.46 | 2.87 | 3.77 | 20.2 °C |
| September | 3.77 | 3.77 | 3.18 | 3.66 | 17.0 °C |
| October | 2.52 | 3.24 | 2.80 | 2.85 | 10.6 °C |
| November | 1.34 | 2.06 | 1.81 | 1.70 | 3.6 °C |
| December snow | 0.95 | 1.70 | 1.53 | 1.30 | -2.7 °C |
| Year | 3.25 avg | 3.05 avg | 968 kWh | 1132 kWh |
Sizing example. To run a 1 kWh-per-day load through December on LiFePO4 batteries (charge controller, battery and inverter losses included) you need about 770 Wp of panels at 70°, versus 910 Wp at 34°. The steep array is 15% smaller for the same winter. Size your own system.
Row spacing in Rumoi
Distance between rows of 2 m long panels (slope length) so that no row shades the next between 10:00 and 14:00 solar time on the winter solstice.
6.0 mrow pitch at 70°
4.8 mrow pitch at 34°
How Rumoi compares in Japan
Against the other 1,215 places in Japan with climate data, for a fixed array at its best angle.
1210thof 1,216 places in Japan for sunshine, shared: 3.25 peak sun hours a day on flat ground.
−12%solar energy a year compared with the average place in Japan: 1,132 against 1,284 kWh per kWp.
+54 mindaylight on the longest day, compared with Tokyo: 15 h 29 min against 14 h 35 min.
34°best year-round tilt here; across Japan it runs from 17° in Miyakojima to 41° in Kushiro.
Of the 1,216 places in Japan, Miyakojima gets the most sun (4.34 peak sun hours a day) and Wakkanai and one other place the least (3.17); Rumoi ranks joint 1210th. In its darkest month, December, 1 kWp of off-grid panels at 70° makes 1.53 kWh a day here, against 2.14 kWh on average in Japan. The shortest day lasts 8 h 54 min, −51 min compared with Tokyo.
Solar forecast for Rumoi, next 48 hours
Expected output of 1 kWp at 70°, computed from the ICON-EU weather model of the Deutscher Wetterdienst (DWD), Europe.
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Questions about the sun in Rumoi
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Places near Rumoi
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A free, live card for Rumoi: where the sun is right now on today's path, a countdown to sunset or sunrise, the daylight change, the moon phase at night and the best panel angle.
Sun positions: NREL Solar Position Algorithm. Climate: NASA POWER monthly climatology (NASA Langley Research Center). Forecast: Deutscher Wetterdienst, ICON-EU (CC BY 4.0), processed. Places: GeoNames (CC BY 4.0). Time zones: IANA. Sources and licences.