Dark Sky Odds

Stargazing at Elan Valley: when is the sky clear and dark?

March is the best month for stargazing at Elan Valley: on average 20 clear, moonless hours of full darkness, and 13% of nights have at least two of them (ERA5, 2006–2025). The darkest spot we found there is darker than 87% of Europe’s land (NASA VIIRS 2025).

How it works ↓

Data updated: 31 December 2025 · Sources and licences

Calculated 5 November 2026 · cloud cover ERA5 2006–2025 · night lights NASA VIIRS 2025

International Dark Sky Park · United Kingdom · DarkSky International

MarchBest month
112Clear moonless dark hours a year
87%darker than … of Europe’s land
13%Nights with ≥ 2 such hours (March)

Month by month

MonthNights with ≥ 2 such hoursClear moonless dark hoursMoonless dark hoursOf them clear
January9%141888%
February9%131439%
March13%2012816%
April13%168419%
May3%32115%
June0%00—
July0%075%
August3%4725%
September8%111159%
October7%101537%
November7%101686%
December6%111886%

No astronomical darkness (June): the Sun stays above −18° all night.

Elan Valley has darkness to spare; what it lacks is clear sky. Come in spring, aim for a moonless night and bring a spare evening: in this part of Wales the clouds decide the outcome more often than the lamps do.

Darkness versus clouds

The International Dark Sky Park is darker than 87% of Europe’s land, with light pollution rated “very dark”. Yet the year adds up to only 112 clear moonless dark hours. Neighbouring Coed y Bont, 18 km away, has the same 112 hours and the same 87%: both places fall within one cell of the cloud-cover calculation (methodology).

Spring windows

In March, 16% of the 128 moonless dark hours are clear, which comes to 20 hours; in April, 16. December delivers 188 hours of darkness, but only 6% are clear, and there are just as few good nights. The next March window: the new moon night of 7–8 March 2027, with 9 moonless dark hours. The Quadrantids on the night of 3–4 January 2027 give a 15% chance of a clear peak night with the Moon at 13%; the Lyrids on 22–23 April offer 28%, but the Moon is 95% lit. Bottom line: March or April, with a second night in reserve; this is the climate of 2006–2025, not a forecast.

Light pollution

Darker than87% of Europe’s land
Light pollutionvery dark (darkest 5–20 %)
Sky-glow index (own, VIIRS) — Darkest spot we found0.35
Sky-glow index (own, VIIRS) — at the official map point0.44
Sky-glow index (own, VIIRS) — median across the area0.45
Darkest spot we found52.292, -3.675 (map) — within 7.6 km of the Wikidata point (no OSM boundary)

Next new moons

New moonNightMoonless dark hours that nightTypical share of good nights that month
9 November 20268–9 November 202610.87%
9 December 20268–9 December 202612.06%
7 January 20277–8 January 202711.89%
6 February 20276–7 February 202710.79%
8 March 20277–8 March 20279.013%
6 April 20276–7 April 20276.513%
6 May 20275–6 May 20273.33%
4 June 20274–5 June 20270.00%
4 July 20273–4 July 20270.00%
2 August 20271–2 August 20272.53%
31 August 202731 August 2027 – 1 September 20276.03%
30 September 202729–30 September 20278.38%

Hours with the Sun below −18° and the Moon below the horizon, on the night of the new moon, at the darkest spot.

Meteor showers

ShowerPeak nightChance of a clear peak nightMoon litMoonless dark hours (Sun < −12°)Radiant max. height
Leonids17–18 November 202613%55%6.860°
Geminids *13–14 December 202612%20%10.871°
Geminids *14–15 December 202612%29%9.571°
Quadrantids3–4 January 202715%13%12.772°
Lyrids22–23 April 202728%95%1.570°
Eta Aquariids *5–6 May 202723%0%5.710°
Eta Aquariids *6–7 May 202715%1%5.59°
Perseids *12–13 August 20278%84%3.267°
Perseids *13–14 August 20275%90%2.067°
Orionids21–22 October 202710%58%2.854°
Leonids17–18 November 202713%82%1.560°
Geminids14–15 December 202712%98%0.071°

* The peak falls in daylight in Europe, so both neighbouring nights are shown.

Clear peak night: at least 2 hours with ≤ 20 % cloud while the Sun is below −12°, on the same calendar night ± 1 in 2006–2025.

How we calculate

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