HF Band & Sunspot Forecaster

UTC --:--:--
Glow intensity reflects live solar flux · red tint reflects live geomagnetic disturbance
📍 Detecting your location…
Based on your IP address, which can be inaccurate for VPNs, corporate networks, or mobile carriers — correct the location and/or ITU Region above if needed. The Day/Night ratings below always use your device's own clock, so they stay accurate regardless of this label.
Solar-Terrestrial Bulletin
Fetching live conditions from NOAA SWPC…
Solar Flux (SFI)
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10.7cm flux · scale runs ~65 (solar minimum) to 300+ (solar maximum)
Planetary K-Index
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geomagnetic activity · scale runs 0 (calm) to 9 (severe storm)
A-Index
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running daily average · scale runs ~0 (calm) to 400 (extreme storm)
Sunspot Number
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latest reported day · higher generally tracks with higher SFI
What the numbers above mean
Solar Flux (SFI)
<80 Low
80–100 Below average
100–150 Moderate
150+ High to very high
K-Index
0–1 Quiet
2–3 Unsettled
4 Active
5–6 Minor–moderate storm
7–9 Severe storm
A-Index
0–7 Quiet
8–15 Unsettled
16–29 Active
30–49 Minor storm
50+ Major–severe storm
NOAA Space Weather Scales — 4-Day Timeline
Scale Today Tomorrow In 2 days In 3 days
R — Radio Blackout
Caused by solar flares; can fade or blackout HF on the sunlit side.
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S — Solar Radiation Storm
Energetic particles from the sun; mainly affects polar-route HF and high-altitude flights.
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G — Geomagnetic Storm
Disturbance in Earth's magnetic field; degrades HF most at high latitudes, can cause aurora.
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How to read the scales above
Each scale runs 1 (minor) to 5 (extreme). "None" is good news — it means conditions are below even the minor threshold, so nothing is currently disrupting propagation from that cause. Read each row left to right as one continuous forecast.
"Today" is NOAA's observed/current level. The next 3 columns for R and S are forecast probabilities (chance of at least minor / chance of major); G's forecast is a direct predicted level. These are forecast odds, not a guarantee.
Band-by-Band Openness Estimate (Mid-Latitude, General Guide)
Frequency ranges shown: ITU Region 2 (Americas) allocation for 40m and 6m (the two bands with clear regional differences); other bands are globally harmonized. Individual countries can add further restrictions beyond their region's general plan — always confirm against your national regulator. You can correct the detected region above in the location panel.
BandFreqDayNight
How to read the Day/Night ratings above
ExcellentBand should be wide open, strong signals likely GoodSolid and workable, normal conditions FairMarginal, may take patience or favor certain paths PoorUnlikely to support contacts, but not impossible ClosedNot expected to support signals right now
Data source: live from NOAA Space Weather Prediction Center public feeds (solar flux, planetary K-index, daily solar indices, space weather scales) — no API key, fetched directly in your browser.
Methodology note: the band-by-band ratings are a simplified educational estimate based on documented relationships between solar flux/MUF, day-night ionospheric layer differences, and geomagnetic-storm absorption — not a full VOACAP-grade path prediction (which needs distance, bearing, season, and time-of-day for a specific circuit). Treat this as a general guide, not a guarantee.
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