Space weather and propagation
Conditions for amateur radio, read from NOAA data. Generated ; this page rebuilds about every three hours. For live graphics — including color maps and the aurora oval — see NOAA's spaceweather.gov. Everything here is also available as plain text and JSON. New to these numbers? Start at the bottom.
Right now
| Measurement | Reading |
|---|---|
| Solar flux (SFI) | 121 — good; the higher bands through 10 m should be workable |
| Sunspot number | 126 sunspots (SESC daily number) |
| Geomagnetic activity (Kp) | Kp 2− (1.67) — quiet — stable HF conditions |
| Solar wind | solar wind 307 km/s (slow); Bz -1.0 nT — slightly southward, north of the −5 nT concern line |
| Latest X-ray flare | C1.1 flare — minor, little HF impact |
Estimated band conditions
A rough guide to the high-frequency bands, day and night, estimated from the solar flux and Kp above — not a measurement. Each rating is shown three ways: the word, a symbol (filled = better), and a color. For what's actually open right now, real-time reports beat any estimate: prop.kc2g.com and PSK Reporter.
| Band | Day | Night |
|---|---|---|
| 80 m | Poor | Good |
| 40 m | Fair | Good |
| 30 m | Good | Good |
| 20 m | Good | Fair |
| 17 m | Good | Closed |
| 15 m | Good | Closed |
| 12 m | Fair | Closed |
| 10 m | Fair | Closed |
VHF: the higher bands don't follow solar flux — they open on sporadic-E and aurora. 6 m — quiet; F2 openings only at very high flux. 2 m — mostly tropo and local.
Radio blackout, radiation, and geomagnetic scales
NOAA rates three kinds of space weather on a 1-to-5 scale; level 0 means none. The scale names are NOAA's; the short radio notes are added here.
- R0 radio blackouts — none; HF is not being degraded by flares.
- S0 solar radiation storms — none.
- G0 geomagnetic storms — none; the geomagnetic field is stable.
Geomagnetic detail
Kp 2− (1.67) — quiet — stable HF conditions.
Kp scale 0 to 9: (2 of 9)
NOAA's storm scale notes how far south aurora has been seen: at Kp 7 (G3), as far as Oregon and Illinois — around 50° geomagnetic latitude; at Kp 6 (G2), New York and Idaho. Below that it stays well to the north.
Aurora power now: northern hemispheric power 18 GW. (Higher power means a brighter, lower-reaching oval.)
Three-day outlook
| Date (UTC) | Highest Kp | Radio-blackout chance | Geomagnetic storm |
|---|---|---|---|
| Sep 23 | 4.33 | 20% | G0 |
| Sep 24 | 5.33 | 20% | G1 |
| Sep 25 | 3.67 | 20% | G0 |
A dash means NOAA's forecast for that measure does not reach that day.
Reading this page
None of the information here depends on color — every reading is written out in words, so it works the same in a screen reader, a text browser, or on paper. Here is what the numbers mean.
- SFI, the solar flux index
- A measure of the Sun's radio output at 10.7 cm, which tracks how well the upper ionosphere reflects signals. Higher generally means the higher HF bands (10, 12, 15 metres) open up. The band interpretations here follow Paul Herrman, N0NBH (hamqsl.com); NOAA publishes the raw number, not the band verdicts.
- Sunspot number
- A daily count of sunspots and sunspot groups. It rises and falls with the roughly 11-year solar cycle and moves with the solar flux.
- Kp, the planetary K-index
- How disturbed Earth's magnetic field is, from 0 (calm) to 9 (extreme storm), averaged over three hours from magnetometers worldwide. Higher Kp means more high-latitude HF trouble and a better chance of aurora. NOAA counts Kp 5 and above as a geomagnetic storm.
- Solar wind and Bz
- The stream of particles from the Sun, and the north–south tilt of the magnetic field it carries (Bz). A southward Bz, roughly −5 nanotesla or lower, lets the solar wind pour energy into Earth's field and drive storms; a northward Bz keeps things quiet.
- WWV
- The time-standard station whose hourly voice bulletins have carried these numbers to operators for decades. NOAA's text version is quoted below, unchanged.
Times on this page are in Coordinated Universal Time (UTC), the standard for space-weather data — the same clock the net's log and most radio operation use.
Latest WWV bulletin
NOAA's geophysical alert, issued 2026-09-23 21:05 UTC, quoted in full:
:Product: Geophysical Alert Message wwv.txt :Issued: 2026 Sep 23 2105 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # # Geophysical Alert Message # Solar-terrestrial indices for 23 September follow. Solar flux 121 and estimated planetary A-index 6. The estimated planetary K-index at 2100 UTC on 23 September was 1.67. No space weather storms were observed for the past 24 hours. Space weather for the next 24 hours is predicted to be minor. Geomagnetic storms reaching the G1 level are likely.
Sources and notice
All data is from NOAA's Space Weather Prediction Center. Each reading is current as of the time shown:
- sfi — source, as of 2026-09-23 20:00 UTC
- ssn — source, as of 2026-09-22 00:00 UTC
- kp — source, as of 2026-09-23 18:00 UTC
- bands — source, as of 2026-09-23 18:00 UTC
- solar wind — source, as of 2026-09-23 21:23 UTC
- scales now — source, as of 2026-09-23 21:32 UTC
- outlook — source, as of 2026-09-23 00:00 UTC
- flare — source, as of 2026-09-23 21:28 UTC
- aurora power — source, as of 2026-09-23 22:46 UTC
- wwv — source, as of 2026-09-23 21:05 UTC
Space-weather data on this page comes from NOAA's Space Weather Prediction Center, a work of the United States Government not subject to copyright (17 U.S.C. § 105); this site's own copyright does not extend to it. Band-condition interpretations for solar flux are Paul Herrman's, N0NBH. This page is not affiliated with or endorsed by NOAA.