Climate and average weather in Piran
In Piran, the summers are humid, warm, fairly dry, and mostly clear and the winters are cool and partly cloudy.
Over the course of the year, the temperature in Piran typically varies from 6°C to 26°C, and is rarely below 2°C or above 29°C. July is the hottest month of the year, while January is the coldest.
Based on the travel score, the best time of year to visit Piran for warm-weather activities is from mid May to late September.
- Hottest
- Jul
- 26°
- Coldest
- Jan
- 6°
- Wettest
- Nov
- 170 mm
- Driest
- Jul
- 47 mm
- Rain / yr
- 1158 mm
- 113 wet days
- Daylight
- 8.5–15.5 h
- shortest–longest
- Elevation
- 0 m
- 45.5°N
- Clearest
- Jul
- 35% cloud
Piran is coastal town of Slovenia.
- Density
- 94/km²
- people per km²
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Piran 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 May to late September.
Temperature through the year
Daily average highs and lows in Piran, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.5 months, from June 5 to September 17, with daily high temperatures above 22°C. The hottest month of the year in Piran is July, with an average high of 26°C and low of 23°C.
The cool season lasts 3.9 months, from November 28 to March 27, with daily high temperatures below 12°C. The coldest month of the year in Piran is January, with an average low of 6°C and high of 9°C.
Days typically run about 2°C warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 9 | 9 | 11 | 14 | 19 | 23 | 26 | 26 | 22 | 18 | 14 | 10 |
| Avg low (°C) | 6 | 6 | 8 | 12 | 16 | 21 | 23 | 23 | 19 | 16 | 12 | 8 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 9 | 6 |
| Feb | 9 | 6 |
| Mar | 11 | 8 |
| Apr | 14 | 12 |
| May | 19 | 16 |
| Jun | 23 | 21 |
| Jul | 26 | 23 |
| Aug | 26 | 23 |
| Sep | 22 | 19 |
| Oct | 18 | 16 |
| Nov | 14 | 12 |
| Dec | 10 | 8 |
Average hourly temperature in Piran
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 July afternoons, near 26°C, and coldest before dawn in January, near 6°C.
Piran weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 9° / 6° | 83 | 9.9 | 0.1 | 8.9 | 1.7 |
| Feb | 9° / 6° | 85 | 8.9 | 0.6 | 10.1 | 1.7 |
| Mar | 11° / 8° | 75 | 8.4 | 0.3 | 11.6 | 2.8 |
| Apr | 14° / 12° | 75 | 9.3 | 0 | 13.2 | 4.3 |
| May | 19° / 16° | 82 | 9.3 | 0 | 14.7 | 6.3 |
| Jun | 23° / 21° | 64 | 7.3 | 0 | 15.4 | 7.6 |
| Jul | 26° / 23° | 47 | 5.6 | 0 | 15.1 | 7.9 |
| Aug | 26° / 23° | 78 | 7 | 0 | 13.9 | 7.7 |
| Sep | 22° / 19° | 142 | 9.6 | 0 | 12.3 | 6.9 |
| Oct | 18° / 16° | 141 | 12.3 | 0 | 10.7 | 5.7 |
| Nov | 14° / 12° | 170 | 13.9 | 0.1 | 9.3 | 3.6 |
| Dec | 10° / 8° | 116 | 11.3 | 0.4 | 8.6 | 2.3 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Piran gets about 1158 mm of precipitation a year. On a typical day the chance of rain is often wet, but that rises and falls sharply with the seasons.
The wetter season lasts 4.4 months, from around Sep 9 to Jan 20, peaking in November at about 47% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jul 23.
November is the wettest month by volume, with 170 mm over about 14 wet days; July is the driest, with 47 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 33 | 32 | 26 | 31 | 30 | 24 | 18 | 22 | 33 | 39 | 45 | 37 |
| Rain days | 10 | 9 | 8 | 9 | 9 | 7 | 6 | 7 | 10 | 12 | 14 | 11 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 33 | 10 |
| Feb | 32 | 9 |
| Mar | 26 | 8 |
| Apr | 31 | 9 |
| May | 30 | 9 |
| Jun | 24 | 7 |
| Jul | 18 | 6 |
| Aug | 22 | 7 |
| Sep | 33 | 10 |
| Oct | 39 | 12 |
| Nov | 45 | 14 |
| Dec | 37 | 11 |
Monthly rainfall
Over a full year, Piran collects about 1158 mm of rain across 113 wet days — roughly 97 mm in an average month.
It doesn’t fall evenly. November is the wettest month with 170 mm, while July is the driest at just 47 mm. The three wettest months alone bring about 39% of the year’s total, and some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 83 | 85 | 75 | 75 | 82 | 64 | 47 | 78 | 142 | 141 | 170 | 116 |
| Rain days | 10 | 9 | 8 | 9 | 9 | 7 | 6 | 7 | 10 | 12 | 14 | 11 |
| Snow days | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Rainfall (mm) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 83 | 10 | 0 |
| Feb | 85 | 9 | 1 |
| Mar | 75 | 8 | 0 |
| Apr | 75 | 9 | 0 |
| May | 82 | 9 | 0 |
| Jun | 64 | 7 | 0 |
| Jul | 47 | 6 | 0 |
| Aug | 78 | 7 | 0 |
| Sep | 142 | 10 | 0 |
| Oct | 141 | 12 | 0 |
| Nov | 170 | 14 | 0 |
| Dec | 116 | 11 | 0 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Piran, 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 8 and lasts for 5.2 months, ending around October 12. The clearest month is July, when the sky is clear, mostly clear, or partly cloudy 79% of the time on average.
The cloudier part of the year begins around October 13 and lasts for 4.9 months, ending around March 10. The cloudiest month is November, when it is overcast or mostly cloudy 59% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 44 | 50 | 57 | 56 | 61 | 71 | 79 | 75 | 64 | 55 | 41 | 43 |
| Cloudier (%) | 56 | 50 | 43 | 44 | 39 | 29 | 21 | 25 | 36 | 45 | 59 | 57 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 44 | 56 |
| Feb | 50 | 50 |
| Mar | 57 | 43 |
| Apr | 56 | 44 |
| May | 61 | 39 |
| Jun | 71 | 29 |
| Jul | 79 | 21 |
| Aug | 75 | 25 |
| Sep | 64 | 36 |
| Oct | 55 | 45 |
| Nov | 41 | 59 |
| Dec | 43 | 57 |
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 June 15, brings about 15 h 30 min of light; the shortest, around December 14, only 8 h 30 min — a swing of roughly 7 hours.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 8.9 | 10.1 | 11.6 | 13.2 | 14.7 | 15.4 | 15.1 | 13.9 | 12.3 | 10.7 | 9.3 | 8.6 |
| Sunrise (AM) | 7:49 | 7:18 | 6:27 | 5:27 | 4:41 | 4:22 | 4:36 | 5:12 | 5:51 | 6:30 | 7:14 | 7:46 |
| Sunset (PM) | 4:41 | 5:23 | 6:03 | 6:44 | 7:23 | 7:50 | 7:46 | 7:08 | 6:09 | 5:11 | 4:28 | 4:18 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 8.9 | 7:49 | 4:41 |
| Feb | 10.1 | 7:18 | 5:23 |
| Mar | 11.6 | 6:27 | 6:03 |
| Apr | 13.2 | 5:27 | 6:44 |
| May | 14.7 | 4:41 | 7:23 |
| Jun | 15.4 | 4:22 | 7:50 |
| Jul | 15.1 | 4:36 | 7:46 |
| Aug | 13.9 | 5:12 | 7:08 |
| Sep | 12.3 | 5:51 | 6:09 |
| Oct | 10.7 | 6:30 | 5:11 |
| Nov | 9.3 | 7:14 | 4:28 |
| Dec | 8.6 | 7:46 | 4:18 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Piran averages about 13 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 8 and 19 days.
The sunnier stretch runs 4.6 months, from around May 18 to Oct 3. The sunniest month is July, with roughly 19 sunny days (bright).
The greyest month is November, down near 9 sunny days — about 54% fewer than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 10 | 10 | 13 | 12 | 13 | 16 | 19 | 19 | 15 | 13 | 8 | 10 |
| Sky | Mixed | Mixed | Mixed | Mixed | Mixed | Bright | Bright | Bright | Bright | Mixed | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 10 | Mixed |
| Feb | 10 | Mixed |
| Mar | 13 | Mixed |
| Apr | 12 | Mixed |
| May | 13 | Mixed |
| Jun | 16 | Bright |
| Jul | 19 | Bright |
| Aug | 19 | Bright |
| Sep | 15 | Bright |
| Oct | 13 | Mixed |
| Nov | 8 | Mixed |
| Dec | 10 | Mixed |
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.
In Piran, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 4.6 months, from around May 20 to October 7. The muggiest month is August, when the air feels humid, muggy or worse about 83% of the time.
The most comfortable stretch runs from around October 8 to May 19, and December is the most comfortable month — the air is dry or comfortable 100% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 100 | 100 | 90 | 42 | 14 | 6 | 5 | 28 | 56 | 87 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 9 | 35 | 18 | 13 | 13 | 22 | 25 | 12 | 0 |
| Humid (%) | 0 | 0 | 0 | 1 | 19 | 30 | 23 | 25 | 30 | 18 | 1 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 5 | 29 | 34 | 33 | 17 | 1 | 0 | 0 |
| Oppressive (%) | 0 | 0 | 0 | 0 | 0 | 9 | 23 | 23 | 3 | 0 | 0 | 0 |
| Miserable (%) | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 100 | 0 | 0 | 0 | 0 | 0 |
| Feb | 100 | 0 | 0 | 0 | 0 | 0 |
| Mar | 100 | 0 | 0 | 0 | 0 | 0 |
| Apr | 90 | 9 | 1 | 0 | 0 | 0 |
| May | 42 | 35 | 19 | 5 | 0 | 0 |
| Jun | 14 | 18 | 30 | 29 | 9 | 0 |
| Jul | 6 | 13 | 23 | 34 | 23 | 2 |
| Aug | 5 | 13 | 25 | 33 | 23 | 2 |
| Sep | 28 | 22 | 30 | 17 | 3 | 0 |
| Oct | 56 | 25 | 18 | 1 | 0 | 0 |
| Nov | 87 | 12 | 1 | 0 | 0 | 0 |
| Dec | 100 | 0 | 0 | 0 | 0 | 0 |
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 Piran is typically light breeze, near 14 km/h, and varies little with the seasons.
The windier part of the year lasts 6.9 months, from around Sep 13 to Apr 10. The windiest month is November, averaging about 16 km/h (light breeze).
The calmer part of the year runs from around Apr 11 to Sep 12, with July the calmest month at about 12 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 15 | 15 | 14 | 13 | 13 | 12 | 12 | 12 | 14 | 15 | 16 | 15 |
| Feels | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | calm | light breeze | light breeze | light breeze | light breeze | light breeze |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 15 | light breeze |
| Feb | 15 | light breeze |
| Mar | 14 | light breeze |
| Apr | 13 | light breeze |
| May | 13 | light breeze |
| Jun | 12 | light breeze |
| Jul | 12 | calm |
| Aug | 12 | light breeze |
| Sep | 14 | light breeze |
| Oct | 15 | light breeze |
| Nov | 16 | light breeze |
| Dec | 15 | light breeze |
Best time to visit Piran
To characterize how pleasant the weather is in Piran throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid September, Piran 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 Piran for general outdoor tourist activities is from mid May to late September, with a peak score in the last week of June.
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) | 1.7 | 1.8 | 2.8 | 4.3 | 6.3 | 7.5 | 7.9 | 7.6 | 6.9 | 5.7 | 3.6 | 2.3 |
| Rating | poor | poor | poor | fair | good | ideal | ideal | ideal | good | good | fair | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 1.7 | poor |
| Feb | 1.8 | poor |
| Mar | 2.8 | poor |
| Apr | 4.3 | fair |
| May | 6.3 | good |
| Jun | 7.5 | ideal |
| Jul | 7.9 | ideal |
| Aug | 7.6 | ideal |
| Sep | 6.9 | good |
| Oct | 5.7 | good |
| Nov | 3.6 | fair |
| Dec | 2.3 | 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 Piran for hot-weather activities is from mid June to early September, with a peak score in the last week of July.
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 Piran, 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.
For a warm-season trip around July (highs near 26°C), the essentials are light clothes and sun protection. In the cold season around January (highs near 9°C), pack a warm layer and rain gear.
In July, Piran sees daytime highs around 26°C and nights near 23°C. Pack sun protection. Worth having: light clothes. About 6 days see rain.
Sea temperature near Piran
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 August at about 25°C and coldest in February near 10°C.
It's comfortable for a long swim from May 31 to Oct 9 — about 4.3 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 11 | 10 | 10 | 13 | 18 | 23 | 25 | 25 | 23 | 19 | 16 | 13 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Warm | Warm | Refreshing | Cool | Cool | Bracing |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 11 | Bracing |
| Feb | 10 | Bracing |
| Mar | 10 | Bracing |
| Apr | 13 | Bracing |
| May | 18 | Cool |
| Jun | 23 | Refreshing |
| Jul | 25 | Warm |
| Aug | 25 | Warm |
| Sep | 23 | Refreshing |
| Oct | 19 | Cool |
| Nov | 16 | Cool |
| Dec | 13 | Bracing |
UV index (midday) in Piran 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 Piran peaks around July 15 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 1 | 2 | 4 | 7 | 7 | 8 | 8 | 7 | 5 | 3 | 2 | 1 |
| Level | Low | Moderate | Moderate | High | High | Very high | Very high | Very high | Moderate | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 1 | Low |
| Feb | 2 | Moderate |
| Mar | 4 | Moderate |
| Apr | 7 | High |
| May | 7 | High |
| Jun | 8 | Very high |
| Jul | 8 | Very high |
| Aug | 7 | Very high |
| Sep | 5 | Moderate |
| Oct | 3 | Moderate |
| Nov | 2 | Low |
| Dec | 1 | Low |
Average hourly UV index in Piran
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 July the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 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) | 0 | 0 | 4 | 6.5 | 7.5 | 8 | 8.5 | 7 | 5.5 | 0 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 2.5 | 3 | 4 | 5 | 3.5 | 0 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 0 | 0 |
| Mar | 4 | 0 |
| Apr | 6.5 | 2.5 |
| May | 7.5 | 3 |
| Jun | 8 | 4 |
| Jul | 8.5 | 5 |
| Aug | 7 | 3.5 |
| Sep | 5.5 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Air quality in Piran 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 Piran is worst in January — around 22 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (September, 12 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 22 | 20 | 20 | 19 | 16 | 16 | 16 | 13 | 12 | 14 | 14 | 18 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 22 | Moderate |
| Feb | 20 | Moderate |
| Mar | 20 | Moderate |
| Apr | 19 | Moderate |
| May | 16 | Moderate |
| Jun | 16 | Moderate |
| Jul | 16 | Moderate |
| Aug | 13 | Moderate |
| Sep | 12 | Moderate |
| Oct | 14 | Moderate |
| Nov | 14 | Moderate |
| Dec | 18 | Moderate |
Growing season
Piran 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 (%) | 99 | 99 | 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 | 99 | 0 |
| Feb | 99 | 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. Piran banks about 2,172 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 0 | 0 | 5 | 88 | 234 | 355 | 440 | 440 | 321 | 209 | 79 | 1 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 5 |
| Apr | 88 |
| May | 234 |
| Jun | 355 |
| Jul | 440 |
| Aug | 440 |
| Sep | 321 |
| Oct | 209 |
| Nov | 79 |
| Dec | 1 |
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.
Piran receives about 3.9 kWh/m² a day of solar energy on average — moderate — with a clear seasonal swing between 1.2 and 6.6 kWh/m².
The brighter stretch of the year lasts 6.0 months, from around Mar 20 to Sep 18. The brightest month is July, averaging about 6.5 kWh/m² (intense).
The dimmest month is December, down near 1.2 kWh/m² — roughly 81% less than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 1.4 | 2.4 | 3.7 | 5.0 | 5.9 | 6.5 | 6.5 | 5.6 | 4.1 | 2.6 | 1.6 | 1.2 |
| Level | Dim | Moderate | Moderate | Bright | Bright | Intense | Intense | Bright | Bright | Moderate | Dim | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 1.4 | Dim |
| Feb | 2.4 | Moderate |
| Mar | 3.7 | Moderate |
| Apr | 5.0 | Bright |
| May | 5.9 | Bright |
| Jun | 6.5 | Intense |
| Jul | 6.5 | Intense |
| Aug | 5.6 | Bright |
| Sep | 4.1 | Bright |
| Oct | 2.6 | Moderate |
| Nov | 1.6 | Dim |
| Dec | 1.2 | Dim |
Where is Piran?
Piran sits at 45.5°N, 13.6°E, 0 m above sea level, in Slovenia. The nearest listed city is Koper, 13 km away.
Topography around Piran
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Piran.
Within 3 km, the terrain around Piran has only modest variations in elevation — a maximum elevation change of 172 m around an average of 10 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 412 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,859 m.
The land around Piran is covered by water (82%) within 3 km, water (65%) and trees (20%) within 16 km, and trees (43%) and water (31%) within 80 km.
Slovenia travel facts
- Travel advisory
- Level 1
- Exercise Normal Precautions
- Power plugs
- Type C / F
- 230 V · 50 Hz
- Prices
- ≈ 63% of US
- price level, 2025
- GDP per capita
- $37,376
- 2025
- Happiness
- 6.9 / 10
- World Happiness, 2025
- Safe drinking water
- 100%
- of population, 2024
- Homicide rate
- 0.6
- per 100k, 2023
- Road deaths
- 5.1
- per 100k/yr, 2019
- Income group
- High
- World Bank
- 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 Piran (45.5278°, 13.5706°, elevation 0 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. 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).