Climate and average weather in Lasem
In Lasem, the weather is muggy, hot, wet, and partly cloudy and remarkably steady, with daytime highs holding near hot levels all year. The wettest stretch peaks around January.
Over the course of the year, the temperature in Lasem typically varies from 24°C to 31°C, and is rarely below 23°C or above 32°C. October is the hottest month of the year, while February is the coldest.
Based on the travel score, the best time of year to visit Lasem for warm-weather activities is from mid June to early October.
- Hottest
- Oct
- 31°
- Coldest
- Feb
- 25°
- Wettest
- Jan
- 284 mm
- Driest
- Aug
- 13 mm
- Rain / yr
- 1749 mm
- 214 wet days
- Daylight
- 11.6–12.4 h
- shortest–longest
- Elevation
- 12 m
- 6.7°S
- Clearest
- Aug
- 45% cloud
Lasem weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around mid June to early October.
Temperature through the year
Daily average highs and lows in Lasem, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
Temperatures in Lasem stay fairly even through the year, without a distinct hot or cool season. The warmest month is October, with an average high of 31°C and low of 25°C; the coolest is February, with an average low of 25°C and high of 29°C.
Days typically run about 5°C warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 29 | 29 | 29 | 30 | 30 | 30 | 30 | 30 | 31 | 31 | 30 | 30 |
| Avg low (°C) | 25 | 25 | 25 | 26 | 26 | 25 | 25 | 24 | 25 | 25 | 25 | 25 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 29 | 25 |
| Feb | 29 | 25 |
| Mar | 29 | 25 |
| Apr | 30 | 26 |
| May | 30 | 26 |
| Jun | 30 | 25 |
| Jul | 30 | 25 |
| Aug | 30 | 24 |
| Sep | 31 | 25 |
| Oct | 31 | 25 |
| Nov | 30 | 25 |
| Dec | 30 | 25 |
How hot and cold Lasem really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, Lasem feels like about 36°C (around April 24). Nearly every day a year carries some heat stress, peaking in April.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 34 | 34 | 35 | 36 | 36 | 34 | 33 | 33 | 34 | 35 | 35 | 35 |
| Air high (°C) | 29 | 29 | 29 | 30 | 30 | 30 | 30 | 30 | 31 | 31 | 30 | 30 |
| Feels-like low (°C) | 25 | 25 | 25 | 25 | 26 | 25 | 25 | 24 | 25 | 25 | 25 | 25 |
| Air low (°C) | 25 | 25 | 25 | 26 | 26 | 25 | 25 | 24 | 25 | 25 | 25 | 25 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 34 | 29 | 25 | 25 |
| Feb | 34 | 29 | 25 | 25 |
| Mar | 35 | 29 | 25 | 25 |
| Apr | 36 | 30 | 25 | 26 |
| May | 36 | 30 | 26 | 26 |
| Jun | 34 | 30 | 25 | 25 |
| Jul | 33 | 30 | 25 | 25 |
| Aug | 33 | 30 | 24 | 24 |
| Sep | 34 | 31 | 25 | 25 |
| Oct | 35 | 31 | 25 | 25 |
| Nov | 35 | 30 | 25 | 25 |
| Dec | 35 | 30 | 25 | 25 |
Average hourly temperature in Lasem
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on October afternoons, near 31°C, and coldest before dawn in February, near 25°C.
Lasem weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 29° / 25° | 284 | 28.9 | 12.3 | 2.9 |
| Feb | 29° / 25° | 249 | 26.4 | 12.2 | 2.9 |
| Mar | 29° / 25° | 231 | 28.1 | 12 | 3.0 |
| Apr | 30° / 26° | 192 | 24.5 | 11.9 | 3.3 |
| May | 30° / 26° | 100 | 16.8 | 11.7 | 4.3 |
| Jun | 30° / 25° | 64 | 10.7 | 11.6 | 5.0 |
| Jul | 30° / 25° | 35 | 5.8 | 11.7 | 5.7 |
| Aug | 30° / 24° | 13 | 3.4 | 11.8 | 5.9 |
| Sep | 31° / 25° | 25 | 4.5 | 12 | 5.4 |
| Oct | 31° / 25° | 87 | 13.2 | 12.1 | 4.3 |
| Nov | 30° / 25° | 189 | 23.4 | 12.3 | 3.2 |
| Dec | 30° / 25° | 281 | 28.3 | 12.4 | 2.9 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Lasem gets about 1749 mm of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 6.3 months, from around Oct 31 to May 11, peaking in January at about 96% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Aug 8.
January is the wettest month by volume, with 284 mm over about 29 wet days; August is the driest, with 13 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 93 | 94 | 91 | 81 | 54 | 36 | 19 | 11 | 16 | 42 | 78 | 91 |
| Rain days | 29 | 26 | 28 | 25 | 17 | 11 | 6 | 3 | 5 | 13 | 23 | 28 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 93 | 29 |
| Feb | 94 | 26 |
| Mar | 91 | 28 |
| Apr | 81 | 25 |
| May | 54 | 17 |
| Jun | 36 | 11 |
| Jul | 19 | 6 |
| Aug | 11 | 3 |
| Sep | 16 | 5 |
| Oct | 42 | 13 |
| Nov | 78 | 23 |
| Dec | 91 | 28 |
Monthly rainfall
Over a full year, Lasem collects about 1749 mm of rain across 214 wet days — roughly 146 mm in an average month.
It doesn’t fall evenly. January is the wettest month with 284 mm, while August is the driest at just 13 mm. The three wettest months alone bring about 47% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 284 | 249 | 231 | 192 | 100 | 64 | 35 | 13 | 25 | 87 | 189 | 281 |
| Rain days | 29 | 26 | 28 | 25 | 17 | 11 | 6 | 3 | 5 | 13 | 23 | 28 |
| Rainfall (mm) | Rain days | |
|---|---|---|
| Jan | 284 | 29 |
| Feb | 249 | 26 |
| Mar | 231 | 28 |
| Apr | 192 | 25 |
| May | 100 | 17 |
| Jun | 64 | 11 |
| Jul | 35 | 6 |
| Aug | 13 | 3 |
| Sep | 25 | 5 |
| Oct | 87 | 13 |
| Nov | 189 | 23 |
| Dec | 281 | 28 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Lasem, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around May 1 and lasts for 6.0 months, ending around October 30. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 69% of the time on average.
The cloudier part of the year begins around October 31 and lasts for 6.0 months, ending around April 30. The cloudiest month is February, when it is overcast or mostly cloudy 92% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 9 | 8 | 18 | 27 | 49 | 59 | 64 | 69 | 62 | 46 | 24 | 9 |
| Cloudier (%) | 91 | 92 | 82 | 73 | 51 | 41 | 36 | 31 | 38 | 54 | 76 | 91 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 9 | 91 |
| Feb | 8 | 92 |
| Mar | 18 | 82 |
| Apr | 27 | 73 |
| May | 49 | 51 |
| Jun | 59 | 41 |
| Jul | 64 | 36 |
| Aug | 69 | 31 |
| Sep | 62 | 38 |
| Oct | 46 | 54 |
| Nov | 24 | 76 |
| Dec | 9 | 91 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around January 1, brings about 12 h 24 min of light; the shortest, around May 29, only 11 h 36 min — a swing of roughly 0 h 48 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 12.3 | 12.2 | 12.0 | 11.9 | 11.7 | 11.6 | 11.7 | 11.8 | 12.0 | 12.1 | 12.3 | 12.4 |
| Sunrise (AM) | 5:33 | 5:42 | 5:42 | 5:39 | 5:40 | 5:46 | 5:50 | 5:45 | 5:30 | 5:15 | 5:10 | 5:19 |
| Sunset (PM) | 5:54 | 5:55 | 5:45 | 5:30 | 5:21 | 5:23 | 5:29 | 5:32 | 5:27 | 5:24 | 5:29 | 5:42 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 12.3 | 5:33 | 5:54 |
| Feb | 12.2 | 5:42 | 5:55 |
| Mar | 12.0 | 5:42 | 5:45 |
| Apr | 11.9 | 5:39 | 5:30 |
| May | 11.7 | 5:40 | 5:21 |
| Jun | 11.6 | 5:46 | 5:23 |
| Jul | 11.7 | 5:50 | 5:29 |
| Aug | 11.8 | 5:45 | 5:32 |
| Sep | 12.0 | 5:30 | 5:27 |
| Oct | 12.1 | 5:15 | 5:24 |
| Nov | 12.3 | 5:10 | 5:29 |
| Dec | 12.4 | 5:19 | 5:42 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Lasem averages about 7 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 0 and 15 days.
The sunnier stretch runs 5.7 months, from around May 9 to Oct 29. The sunniest month is September, with roughly 13 sunny days (mixed).
The greyest month is February, down near 0 sunny days — about 96% fewer than the September peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 1 | 0 | 2 | 4 | 9 | 11 | 13 | 15 | 13 | 9 | 4 | 1 |
| Sky | Gloomy | Gloomy | Gloomy | Gloomy | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Gloomy | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 1 | Gloomy |
| Feb | 0 | Gloomy |
| Mar | 2 | Gloomy |
| Apr | 4 | Gloomy |
| May | 9 | Mixed |
| Jun | 11 | Mixed |
| Jul | 13 | Mixed |
| Aug | 15 | Mixed |
| Sep | 13 | Mixed |
| Oct | 9 | Mixed |
| Nov | 4 | Gloomy |
| Dec | 1 | Gloomy |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
Lasem is humid all year round — on a typical day the air feels at least humid, and there is no real dry season to wait for.
The stickiest month is January, when it feels muggy, oppressive or miserable about 100% of the time. Even in January, the mildest month, the air is dry or comfortable only 0% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Humid (%) | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 | 1 | 0 | 0 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 2 | 10 | 30 | 40 | 29 | 7 | 0 | 0 |
| Oppressive (%) | 64 | 59 | 44 | 27 | 40 | 63 | 62 | 55 | 66 | 80 | 64 | 55 |
| Miserable (%) | 36 | 41 | 56 | 73 | 58 | 27 | 7 | 2 | 4 | 13 | 36 | 45 |
| Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|
| Jan | 0 | 0 | 64 | 36 |
| Feb | 0 | 0 | 59 | 41 |
| Mar | 0 | 0 | 44 | 56 |
| Apr | 0 | 0 | 27 | 73 |
| May | 0 | 2 | 40 | 58 |
| Jun | 0 | 10 | 63 | 27 |
| Jul | 1 | 30 | 62 | 7 |
| Aug | 3 | 40 | 55 | 2 |
| Sep | 1 | 29 | 66 | 4 |
| Oct | 0 | 7 | 80 | 13 |
| Nov | 0 | 0 | 64 | 36 |
| Dec | 0 | 0 | 55 | 45 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Lasem is typically calm, near 10 km/h, and varies moderately with the seasons.
The windier part of the year lasts 2.4 months, from around Dec 23 to Mar 5. The windiest month is January, averaging about 13 km/h (light breeze).
The calmer part of the year runs from around Mar 6 to Jun 10, with April the calmest month at about 8 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 13 | 13 | 9 | 8 | 9 | 11 | 12 | 12 | 11 | 9 | 8 | 10 |
| Feels | light breeze | light breeze | calm | calm | calm | calm | calm | light breeze | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 13 | light breeze |
| Feb | 13 | light breeze |
| Mar | 9 | calm |
| Apr | 8 | calm |
| May | 9 | calm |
| Jun | 11 | calm |
| Jul | 12 | calm |
| Aug | 12 | light breeze |
| Sep | 11 | calm |
| Oct | 9 | calm |
| Nov | 8 | calm |
| Dec | 10 | calm |
Hazard calendar for Lasem
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Lasem sits in the South Indian Ocean cyclone belt; the season peaks January–March.
Lasem's rainy season runs November–April, when most of the year's rain falls.
Best time to visit Lasem
To characterize how pleasant the weather is in Lasem throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around late September, Lasem is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best time of year to visit Lasem for general outdoor tourist activities is from mid June to early October, with a peak score in the first week of August.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 2.9 | 2.9 | 3.0 | 3.3 | 4.3 | 5.0 | 5.7 | 5.9 | 5.4 | 4.3 | 3.2 | 2.9 |
| Rating | poor | poor | poor | poor | fair | fair | good | good | fair | fair | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 2.9 | poor |
| Feb | 2.9 | poor |
| Mar | 3.0 | poor |
| Apr | 3.3 | poor |
| May | 4.3 | fair |
| Jun | 5.0 | fair |
| Jul | 5.7 | good |
| Aug | 5.9 | good |
| Sep | 5.4 | fair |
| Oct | 4.3 | fair |
| Nov | 3.2 | poor |
| Dec | 2.9 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best time of year to visit Lasem for hot-weather activities is from mid June to mid October, with a peak score in the second week of August.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Lasem, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
Lasem packs about the same all year — highs hold near 31°C. Across the year the things worth having are light clothes, rain gear and sun protection.
In October, Lasem sees daytime highs around 31°C and nights near 25°C. Pack light clothes and sun protection. Worth having: rain gear. About 13 days see rain.
Sea temperature near Lasem
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea offshore is warmest in November at about 30°C and coldest in August near 28°C.
The water stays above 20°C all year — warm enough for a swim any month.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 29 | 29 | 29 | 30 | 30 | 29 | 29 | 28 | 29 | 29 | 30 | 30 |
| Comfort | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 29 | Tropical |
| Feb | 29 | Tropical |
| Mar | 29 | Tropical |
| Apr | 30 | Tropical |
| May | 30 | Tropical |
| Jun | 29 | Tropical |
| Jul | 29 | Tropical |
| Aug | 28 | Tropical |
| Sep | 29 | Tropical |
| Oct | 29 | Tropical |
| Nov | 30 | Tropical |
| Dec | 30 | Tropical |
UV index (midday) in Lasem by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Lasem peaks around March 17 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 16 at about 8 (very high).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 10 | 10 | 14 | 11 | 9 | 8 | 9 | 11 | 12 | 12 | 7 | 11 |
| Level | Extreme | Extreme | Extreme | Extreme | Very high | Very high | Very high | Extreme | Extreme | Extreme | Very high | Extreme |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 10 | Extreme |
| Feb | 10 | Extreme |
| Mar | 14 | Extreme |
| Apr | 11 | Extreme |
| May | 9 | Very high |
| Jun | 8 | Very high |
| Jul | 9 | Very high |
| Aug | 11 | Extreme |
| Sep | 12 | Extreme |
| Oct | 12 | Extreme |
| Nov | 7 | Very high |
| Dec | 11 | Extreme |
Average hourly UV index in Lasem
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in March the burn window is concentrated in the middle of the day: about 8 hours a day reach index 3 (protection recommended), and 6.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 7.5 | 7.5 | 8 | 7.5 | 7 | 6.5 | 7 | 7.5 | 8 | 8 | 7 | 8 |
| UV ≥ 6 (h/day) | 5.5 | 5.5 | 6.5 | 5.5 | 4.5 | 3.5 | 4.5 | 5.5 | 6 | 5.5 | 4 | 5.5 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 7.5 | 5.5 |
| Feb | 7.5 | 5.5 |
| Mar | 8 | 6.5 |
| Apr | 7.5 | 5.5 |
| May | 7 | 4.5 |
| Jun | 6.5 | 3.5 |
| Jul | 7 | 4.5 |
| Aug | 7.5 | 5.5 |
| Sep | 8 | 6 |
| Oct | 8 | 5.5 |
| Nov | 7 | 4 |
| Dec | 8 | 5.5 |
Air quality in Lasem by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Lasem is worst in May — around 40 µg/m³ PM2.5 (poor), and holds fairly steady the rest of the year.
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 27 | 25 | 32 | 35 | 40 | 37 | 34 | 33 | 35 | 39 | 34 | 30 |
| Level | Moderate | Moderate | Moderate | Poor | Poor | Poor | Moderate | Moderate | Poor | Poor | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 27 | Moderate |
| Feb | 25 | Moderate |
| Mar | 32 | Moderate |
| Apr | 35 | Poor |
| May | 40 | Poor |
| Jun | 37 | Poor |
| Jul | 34 | Moderate |
| Aug | 33 | Moderate |
| Sep | 35 | Poor |
| Oct | 39 | Poor |
| Nov | 34 | Moderate |
| Dec | 30 | Moderate |
Growing season
Lasem is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 100 | 0 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Lasem banks about 6,371 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around October.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 530 | 478 | 537 | 528 | 550 | 523 | 532 | 533 | 529 | 556 | 534 | 540 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 530 |
| Feb | 478 |
| Mar | 537 |
| Apr | 528 |
| May | 550 |
| Jun | 523 |
| Jul | 532 |
| Aug | 533 |
| Sep | 529 |
| Oct | 556 |
| Nov | 534 |
| Dec | 540 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Lasem receives about 5.6 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 4.9 and 6.8 kWh/m².
The brighter stretch of the year lasts 4.1 months, from around Jul 23 to Nov 24. The brightest month is September, averaging about 6.7 kWh/m² (intense).
The dimmest month is January, down near 5.0 kWh/m² — roughly 26% less than the September peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 5.0 | 5.1 | 5.5 | 5.4 | 5.3 | 5.1 | 5.5 | 6.2 | 6.8 | 6.7 | 5.9 | 5.1 |
| Level | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Intense | Intense | Intense | Bright | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 5.0 | Bright |
| Feb | 5.1 | Bright |
| Mar | 5.5 | Bright |
| Apr | 5.4 | Bright |
| May | 5.3 | Bright |
| Jun | 5.1 | Bright |
| Jul | 5.5 | Bright |
| Aug | 6.2 | Intense |
| Sep | 6.8 | Intense |
| Oct | 6.7 | Intense |
| Nov | 5.9 | Bright |
| Dec | 5.1 | Bright |
Where is Lasem?
Lasem sits at 6.7°S, 111.5°E, 12 m above sea level, in Indonesia. The nearest listed city is Rembangan, 12 km away.
Topography around Lasem
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Lasem.
Within 3 km, the terrain around Lasem has significant variations in elevation — a maximum elevation change of 251 m around an average of 28 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 787 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,559 m.
The land around Lasem is covered by trees (38%) and cropland (21%) within 3 km, water (40%) and trees (34%) within 16 km, and water (36%), trees (35%) and cropland (24%) within 80 km.
Indonesia travel facts
- Travel advisory
- Level 2
- Exercise Increased Caution
- Power plugs
- Type C / F
- 230 V · 50 Hz
- Prices
- ≈ 29% of US
- price level, 2025
- GDP per capita
- $5,060
- 2025
- Happiness
- 5.6 / 10
- World Happiness, 2025
- Safe drinking water
- 30%
- of population, 2024
- Homicide rate
- 0.3
- per 100k, 2022
- Road deaths
- 11.3
- per 100k/yr, 2019
- Income group
- Upper middle
- World Bank
- English
- Low
- EF EPI 471
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Lasem (-6.6922°, 111.4527°, elevation 12 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).