Postojna weather in May

In May, Postojna sees average daytime highs of 18°C and overnight lows near 10°C, with 142 mm of rain across 14.8 wet days and about 14.7 hours of daylight. It is the 5th-warmest and 5th-wettest month of the year here.

Highs climb over the month, from about 17°C in the first days to 20°C by the end. The sky is clear or mostly clear about 28% of the time in May, and the air most often feels dry.

Daylight stretches from about 14 h 06 min at the start of May to 15 h 12 min by month's end. Set against the rest of the year, May is Postojna's 5th-clearest and 8th-windiest month. For the whole year in context, see Postojna's year-round climate.

Daytime high
18°
5th warmest
Overnight low
10°
8th coldest
Rainfall
142 mm
14.8 wet days
Daylight
14 h 42 min
4:38 AM – 7:21 PM
Cloud cover
60%
5th clearest
Wind
8 km/h
8th windiest
Solar energy
5.54 kWh/m²
Travel score
5.3
out of 10

Postojna is city in Slovenia.

Density
288/km²
people per km²

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 17°C in the first days to 20°C by the end.

A typical May day in Postojna reaches about 18°C in the afternoon and slips back to 10°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 14°C and 23°C. Set against its neighbours, May runs about 4°C warmer than April and about 4°C cooler than June.

10°20°30°151015202531
Avg high (°C)Avg low (°C)
1178
2178
3178
4178
5178
6178
7178
8189
9189
10189
11189
12189
13189
14189
15189
16189
171810
181910
191910
201910
211910
221910
231910
241910
252011
262011
272011
282011
292011
302011
312011

How May really feels in Postojna

Once humidity and wind are folded in, May averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

May sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Postojna weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -3°909.95.38.90.0
Feb / -2°106105.310.10.2
Mar / 10611.13.711.62.0
Apr14° / 12213.71.213.33.7
May18° / 10°14214.8014.75.3
Jun22° / 13°13714.4015.56.1
Jul25° / 15°12212.7015.26.8
Aug24° / 15°14512.4013.96.7
Sep19° / 11°17612.1012.35.8
Oct14° / 14812.10.410.74.0
Nov / 17212.62.39.31.5
Dec / -2°12210.34.48.50.0

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 28% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 20% of May, with mostly cloudy or overcast conditions the remaining 52%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14555
24654
34555
44654
54654
64654
74654
84654
94753
104753
114753
124753
134753
144753
154852
164852
174951
184951
195050
205050
215050
225050
235050
245050
255050
265050
275050
284951
294951
304852
314852

Chance of precipitation in May

Any precipitation

Postojna gets around 142 mm of rain over 14.8 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 48% and peaks near 50% on the wettest days.

0%20%40%60%151015202531
Rain chance (%)
149
249
349
450
550
650
749
849
949
1049
1149
1249
1349
1449
1549
1648
1748
1848
1947
2047
2147
2247
2347
2447
2547
2648
2748
2848
2949
3049
3149

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

Most of May feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, May lands in the dry band about 90% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
19910
29910
39910
49910
59910
69820
79820
89820
99820
109730
119730
129730
139640
149640
159550
169460
179460
189370
199280
209190
2188111
2287121
2386131
2484151
2582171
2679192
2777212
2875232
2971263
3069283
3166313

Wind in May

Winds average 8 km/h in May.

Across May, daily wind ranges from about 8 km/h on the calmest days to 8 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
238calm
248calm
258calm
268calm
278calm
288calm
298calm
308calm
318calm

Sunrise & sunset in May

DaylightNight

Daylight runs from about 14 h 06 min at the start of May to 15 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 66 minutes over May. Sunrise moves from 4:59 AM to 4:24 AM, and sunset from 7:02 PM to 7:37 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.14:597:02
214.14:577:03
314.14:567:05
414.24:547:06
514.24:537:07
614.34:517:08
714.34:507:10
814.44:487:11
914.44:477:12
1014.54:457:14
1114.54:447:15
1214.64:437:16
1314.64:427:17
1414.64:407:18
1514.74:397:20
1614.74:387:21
1714.84:377:22
1814.84:367:23
1914.84:347:24
2014.94:337:26
2114.94:327:27
2214.94:317:28
2315.04:307:29
2415.04:297:30
2515.04:297:31
2615.14:287:32
2715.14:277:33
2815.14:267:34
2915.24:257:35
3015.24:257:36
3115.24:247:37

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.54 kWh/m².

For context, solar energy here swings from a low near 1.07 kWh/m² to a high of 6.11 kWh/m² in July across the year — May's 5.54 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.1Bright
25.2Bright
35.2Bright
45.2Bright
55.2Bright
65.3Bright
75.3Bright
85.3Bright
95.3Bright
105.3Bright
115.4Bright
125.4Bright
135.4Bright
145.4Bright
155.5Bright
165.5Bright
175.5Bright
185.5Bright
195.6Bright
205.6Bright
215.6Bright
225.7Bright
235.7Bright
245.7Bright
255.8Bright
265.8Bright
275.8Bright
285.8Bright
295.8Bright
305.9Bright
315.9Bright
Planning a trip in May

Is May a good time to visit Postojna?

Our two travel scores rate May for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.3
Sightseeing
5th-best month of the year
2.0
Beach & pool
5th-best month of the year

May is a reasonable time to visit Postojna for sightseeing.

What to pack for Postojna in May

From May's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In May, Postojna sees daytime highs around 18°C and nights near 10°C. Pack rain gear. Worth having: sun protection. About 15 days see rain.

rain gearsun protection

Sea temperature near Postojna in May

The nearest coast averages about 17°C in May — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 46 km away) is warmest in August at about 23°C and coldest in February near 10°C.

It's comfortable for a long swim from Jun 10 to Sep 22 — about 3.5 months when the water holds above 20°C.

10°15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan10Bracing
Feb10Bracing
Mar10Bracing
Apr12Bracing
May17Cool
Jun21Refreshing
Jul23Refreshing
Aug23Refreshing
Sep21Refreshing
Oct18Cool
Nov15Cool
Dec12Bracing

UV index in Postojna in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Postojna peaks around July 16 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 10 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 16UV 9Jan 10UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar5Moderate
Apr7Very high
May7High
Jun8Very high
Jul9Very high
Aug8Very high
Sep5High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Postojna in May

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where May falls, not just the annual average.

Air quality in Postojna is worst in January — around 19 µg/m³ PM2.5 (moderate), and holds fairly steady the rest of the year.

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateJan 1918 µg/m³Sep 1512 µg/m³
PM2.5 (µg/m³)Level
Jan19Moderate
Feb17Moderate
Mar18Moderate
Apr18Moderate
May15Moderate
Jun16Moderate
Jul14Moderate
Aug13Moderate
Sep12Good
Oct13Moderate
Nov13Moderate
Dec15Moderate
Location & terrain

Where is Postojna?

Postojna sits at 45.8°N, 14.2°E, 0 m above sea level, in Slovenia. The nearest listed city is Divača, 21 km away.

DivačaTriesteLjubljanaKoperNova GoricaGoriziaKranjRijeka

Topography around Postojna

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Postojna.

Within 3 km, the terrain around Postojna has significant variations in elevation — a maximum elevation change of 409 m around an average of 606 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 1,054 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,695 m.

The land around Postojna is covered by trees (69%) and grassland (20%) within 3 km, trees (77%) within 16 km, and trees (70%) within 80 km.

3 km
409 m
16 km
1,054 m
80 km
2,695 m
treesgrasslandcroplandartificial surfaceswaterwetland
May weather nearby: Divača 21 km · Trieste 37 km · Ljubljana 38 km · Koper 45 km · Nova Gorica 48 km · Gorizia 50 km · Kranj 53 km · Rijeka 53 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
Catholic 69%atheist 14%Orthodox 4%non-believer/agnostic 4%

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 Postojna (45.7743°, 14.2153°, 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).