Bulgaria · The summary is refreshed every 15 minutes.
No current value: fewer than four sensors at different places are reporting now.
Sliven, October 21, 2026: daily mean PM2.5 10 µg/m³ (5 sensors), level “Low” — as in the Atmy Data Hub. Open methodology and data in JSON: Methodology and data sources · JSON
In Sliven the air is moderate right now (approximate, US EPA scale). From 08:00 to 19:00 local time the city mean PM2.5 fell from 19.6 to 14.0 µg/m³. The highest hour was 12:00 with 25.8 µg/m³.
Light wind (1 m/s) in the evening or at night, as the air cools, possibly traps particles near the ground (a temperature inversion).
Weather now: partly cloudy, 17°C, wind 1 m/s, humidity 79%. By 07:00 the wind is expected to pick up to 4 m/s, which may clear the air. Precipitation is expected around 07:00; it may wash particles out. By 08:00 the temperature will be about 14°C.
Written automatically at 20:07 local time (17:07 UTC) from sensor measurements and the weather forecast. Values are approximate; hypotheses are marked.
4 km/h
Wind, ENE
0.2 mm
Precipitation today
10 µg/m³ Low
Daily mean PM2.5 on October 21, 2026 (00:00–24:00 UTC): 10 µg/m³ from 5 sensors that passed the quality check — the same value as in the Atmy Data Hub.
Monthly means of quality-checked sensors, as in the Data Hub trend; the current month is still incomplete, “-” means no data.
20%An estimate of weather conditions · not a PM2.5 forecast
19°/12°
Index by time of day
55/100Moderate
Night
Morning
Day
Evening18°/10°
Index by time of day
41/100Moderate
NightMorningDayEvening17°/7°
Index by time of day
56/100Moderate
NightMorningDayEvening16°/10°
Index by time of day
52/100Moderate
NightMorningDayEvening19°/9°
Index by time of day
50/100Moderate
NightMorningDayEvening16°/8°
Index by time of day
38/100Moderate
NightMorningDayEveningForecast of conditions that trap pollution near the surface
17°
Partly cloudy. Feels like 17°C
13°C79%
18°C65%15°C83%4km/hWind from the ENE
7km/hWind gusts
Wind force: 1
Light wind is expected over the next few hours.
Bulgaria
19°C12°C18°C10°C17°C7°C16°C10°C19°C9°C16°C8°C
14°C6°C15°C5°C14°C6°C12°C5°C475
SofiaBulgaria
252PlovdivBulgaria
42VarnaBulgaria
25Cities with the most sensors
All sensors on the map, by city as the map assigns them; the city’s values count only the sensors that pass the Data Hub’s quality check.
Daily mean PM2.5 of the city sensors, µg/m³
Click a day to see its date and value.
Bulgaria · City ranking · All pilot cities
Daily mean PM2.5 on October 21, 2026 (00:00–24:00 UTC): 10 µg/m³ from 5 sensors that passed the quality check — the same value as in the Atmy Data Hub. No. 10 of 20 cities in Bulgaria and No. 111 of 297 worldwide, from the most polluted.
Fresh data for Sliven are insufficient (last update: 16:00 local time, 13:00 UTC). Open the map for the latest readings of individual sensors.
From Atmy sensors and connected public networks (citizen, experimental and government monitors), aggregated by Atmy. Values are approximate; see the methodology.
The summary is rebuilt every 15 minutes from the latest reading of each sensor, each no older than one hour.
Over the last 159 days with data, the mean daily PM2.5 in Sliven was 5.7 µg/m³ — 1.1 times the WHO annual guideline (5 µg/m³). Over the last 30 days: 3.5 µg/m³. From Atmy's archive of daily city means.
In Atmy's daily archive, the cleanest month of the last year was September 2026: 2.4 µg/m³ on average.
The most polluted month of the last year was December 2025: 11.8 µg/m³ on average.
The daily value is the Data Hub’s: the mean of the city’s sensors that passed the nightly quality check, each with at least 12 valid hours, and only with sensors at four places 500 m apart; days are UTC.
“Now” uses the same sensors and rule: the mean of their latest readings, each at most 60 minutes old, shown only with sensors at four places 500 m apart reporting.
Source: public Atmy monitoring data. Methodology and data sources · Data terms
