Northern Lights tonight in Radnor, PA

Tonight in Radnor

Radnor sits at a geomagnetic latitude of 49.2° N, so the aurora usually needs a Kp index of about 7 or higher before it rises above the northern horizon. Tonight's NOAA forecast peaks at Kp 3 (quiet) during the dark hours, 4.0 short of what Radnor needs.

Open-Meteo expects about 0% cloud cover on average between 8 pm and 7 am local time, with 11 of 11 dark hours mostly clear (30% cloud or less).

The Moon is 100% illuminated (full moon), bright enough to wash out a faint aurora, so only a stronger display will stand out. For the best view look north, low on the horizon, from somewhere away from street lights.

Right now NOAA's OVATION model gives up to 0% chance of aurora in the part of the sky visible from Radnor. OVATION is a short-range nowcast (30 to 90 minutes ahead), useful for deciding whether to step outside now.

3-day Kp forecast

None of the next 3 days reaches the Kp 7 that Radnor needs. Kp is a global 0–9 index of geomagnetic activity, issued in 3-hour blocks (UTC); NOAA forecasts beyond 24 hours are uncertain, because storms are triggered by solar eruptions that take 1–3 days to arrive.

Why Radnor needs Kp 7

The aurora forms in an oval around the geomagnetic pole, which sits in the Canadian Arctic (about 80.8° N, 72.8° W), not at the geographic pole. That is why North American cities see aurora further south than European cities at the same latitude. At Kp 0 the oval's edge is near 66° geomagnetic; each step of Kp pushes it roughly 2° toward the equator.

At 49.2° geomagnetic, Radnor needs about Kp 7 for aurora low on the horizon, Kp 9 or more for a display high in the sky.

Aurora forecast for nearby cities

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• Northern lights Camden

More sky and weather

• Aurora forecast (all cities)
• Northern Taurids meteor shower
• Meteor showers
• Weather warnings