Seismic events and radiation levels, from the two sources that are public and near real time.
What it is. The U.S. Geological Survey runs the national earthquake monitoring system and pulls in seismometers from around the world. It publishes every earthquake it detects, worldwide, usually within minutes, as a free public feed.
Why we use it. It is the fastest public signal. A large explosion shakes the ground like an earthquake, so it shows up here within minutes, hours before anything could reach us through the air. It gives the time, place, size and depth. That lets us see how far an event is from home and the routes, and whether it is near a known nuclear test site.
Its limit. Its first, automatic report calls almost everything an earthquake. USGS labels an event an "explosion" only after analysts review it, sometimes hours later, and an air burst may not register at all. That is why we also watch radiation.
What it is. The Environmental Protection Agency's national radiation monitoring network. It has fixed air monitors in cities in every state, measuring gamma radiation around the clock and publishing hourly readings free to the public.
Why we use it. It answers the question that changes decisions: is radiation rising here, or heading this way? We track every monitor in Tennessee, Arkansas, Oklahoma and Texas, plus the monitors upwind of both routes. Weather usually moves west to east, so a real rise would show up at the western monitors first. Each monitor is compared with its own normal level, and alerts go to your phone and email if any reaches the alarm level.
Its limit. It is slower: EPA posts hourly readings, often an hour or more late, and airborne material takes hours to days to travel. Rain also causes harmless short spikes.
Together: USGS is the early heads-up that something may have happened; RadNet confirms whether it matters where we are. Neither one is an official warning. Wireless Emergency Alerts on your phone and local radio come first.
Background indicators for the USA, Europe and Japan. These are not live measurements like the earthquake and radiation data below. Each card says who publishes the level, whether it is official, and links to the source, so you always see today's figure rather than a copy that may be out of date.
The scale, for reference: 5 is normal peacetime readiness, 1 is nuclear war imminent. No level is marked because the real one is not public.
The real DEFCON level is classified. The Pentagon does not announce changes; the last one confirmed publicly was DEFCON 3 on 11 September 2001. DEFCON is a US-only system: Europe and Japan do not have one, and NATO's own alert states are also secret.
A private group of open-source analysts publishes an estimate, including separate figures for the US commands that cover Europe (EUCOM) and the Indo-Pacific (INDOPACOM). Treat it as informed guesswork.
DEFCON estimate at defconlevel.com ↗National Terrorism Advisory System, from the Department of Homeland Security. When there is a specific or general threat to the US, DHS issues a public Bulletin, or an Alert (Elevated or Imminent), each with an expiry date. When nothing is in effect, the page says so.
Current NTAS advisory at dhs.gov ↗Also on your phone: Wireless Emergency Alerts, the official channel for an attack or radiation warning in your area.
There is no single public threat level for Europe. The clearest official one is the UK national terrorism threat level, set by MI5 on a five-step scale:
It covers terrorism, not war. NATO's military alert states are not published.
Current UK threat level at mi5.gov.uk ↗Japan has no standing threat level. Instead it has J-Alert, the government's national warning system. It sends missile and attack warnings straight to phones, TV and town loudspeakers in the areas at risk, usually within minutes of a launch. The Ministry of Defense then publishes details of each North Korean launch.
How J-Alert works (Cabinet Secretariat, PDF) ↗ Japan Ministry of Defense ↗Set by the Bulletin of the Atomic Scientists on 27 January 2026, the closest to midnight it has ever been. It is reset once a year, usually in late January. It reflects expert judgment of nuclear, climate and technology risk, not a military readiness level.
Doomsday Clock at thebulletin.org ↗This example assumes home is in Knoxville, close to the Oak Ridge nuclear-weapons complex, a likely target. The plan is to use one of the two routes to Mena early, before anything happens, not in the minutes after a warning. This board puts your own triggers next to the live signals on this page and suggests which of the three situations you are in. It is a guide for your judgment: official instructions (Wireless Emergency Alerts, local radio) always come first.
Days to hours before anything happens. The best use of the routes.
Minutes of warning. Do not drive: you would not get clear, and a car gives almost no protection.
You have sheltered through the first danger. Now decide when to move.
Guidance based on ready.gov/radiation and FEMA's planning guidance for a nuclear detonation ("get inside, stay inside, stay tuned").
Every earthquake the USGS has recorded worldwide in the last 24 hours, above the magnitude you pick. An underground or ground-level explosion registers here within minutes, but so does every ordinary earthquake. USGS first reports nearly everything as an earthquake and relabels an event "explosion" only after review. When it does, the row says so in red. Narrow the list to the regions that matter and the noise drops sharply.
| When (local) | Mag | Depth | Place | ||
|---|---|---|---|---|---|
| Loading… | |||||
Amber marks an event that is both shallow (10 km or less) and M4.0 or above — unusual for a natural quake, and what an explosion looks like on a seismograph. Red marks one within 95 miles of a declared or former nuclear test site: Nevada, Novaya Zemlya, Lop Nur, Punggye-ri, Semipalatinsk, Pokhran, Ras Koh. Both are prompts to go and check other sources, not conclusions — earthquakes happen near test sites too, and most of these regions are seismically active anyway. Note that the Europe and Russia boxes overlap over western Russia, which is in both.
Every EPA radiation monitor in the country, checked for the alarm level. If any of them reaches it, the red banner at the top of this page and the phone and email alert name the city and state, and say how far it is and in which direction from home (Knoxville in this example). Monitors much higher than their own normal level are also flagged here. That is more often rain or a fault than anything real, so they don't trigger an alert.
If the bases near the routes were hit, the fallout would go where the wind above them takes it. This panel shows that wind, now and for the next 24 hours, at each base. It says whether it is blowing toward the route, how long fallout would take to arrive, and what the radiation monitors under that path are reading.
Route A is fastest but runs through Nashville, Memphis and Little Rock, and passes about 15 miles from Little Rock AFB. Route B avoids every large city and that base, at the cost of two-lane roads and more time. Route C stays north of the whole I-40 corridor, keeping about 45 miles from Little Rock AFB and well away from Barksdale. It is the longest, crosses the Ohio and Mississippi at Cairo, passes about 15 miles from Fort Campbell, and runs closer to Whiteman AFB's side of the map. Which route is safest depends on the wind that day, which is what this panel shows. Drive times come from TomTom with live traffic, refreshed every 15 minutes, using this site's own TomTom key (your own Watch gets its own free key, which we help you set up). Both routes are on the map, and each target shows its verdict for all three (A, B, C). Pick a route: the chances and the fallout table below follow it.
Targets modelled for this corridor. Oak Ridge (Y-12 weapons complex, at the start), Redstone Arsenal (Huntsville, near Route B), Little Rock AFB (beside Route A), Tinker AFB (upwind of Mena), Barksdale AFB (south of Mena) and Whiteman AFB (north-west). Any of them could send fallout across a route, depending on the wind. Your own Watch models the targets around your own home and routes.
If a base were hit at that hour, how likely is it that its fallout would cross the road? This is not the chance of an attack. It uses that hour's forecast wind plus how uncertain the forecast is. The uncertainty grows the further ahead you look, is larger when the winds at different heights disagree, and is larger again when the wind is light. "Any of them" treats the targets as independent.
What radiation level each town on the route would see, hour by hour, if the bases you tick were hit by ground bursts, carried by the forecast wind at that time. It uses WSEG-10, the standard US civil-defense fallout model, and the "mean case" it predicts. Real fallout can be several times higher or lower, and a wind shift moves the plume entirely. Weapon size is an assumption; change it below. Weapons exploded in the air leave very little local fallout, so these figures are the heavy case.
What the numbers mean for you. Staying inside cuts the dose a great deal. A car blocks almost nothing; a house cuts it roughly 2–3×; a basement roughly 10×; the middle of a large building's basement, 100× or more. Dose rate falls about tenfold for every sevenfold increase in time: at 7 hours it is a tenth of the 1-hour level, at 2 days a hundredth. That is why sheltering first and driving later is almost always safer than driving through a plume. The "dose to 48 h" column assumes you are outdoors the whole time from when fallout arrives. Model: WSEG-10 (Hanifen, AFIT 1980), ported from the MIT-licensed glasstone library; 50% fission yield; dose rate falls as t−1.2.
How to read it. "Fallout wind" is the average of the winds at about 5,000, 10,000 and 18,000 ft (850, 700 and 500 hPa). That is the layer that carries most fallout from a ground-level burst. Surface wind is shown too, but it matters less. The panel checks the fallout wind against every point along the selected route, from Knoxville to Mena. HIT means it points within 25° of the road, so fallout from that base would cross the route. NEAR MISS means within 50°, so the edge of a spreading plume could reach it. MISS means it is blowing away from the road. The "next 24 h" strip shows how that is expected to change as the wind shifts. Real plumes spread and curve as the wind changes, so treat the arrival times as rough. Rain along the path brings fallout down faster and heavier where it falls. It also causes the harmless radon spikes on the radiation charts, so rain is shown on each card. This panel is a planning aid, not a fallout forecast. After a real attack, follow official instructions.
Weather data by Open-Meteo.com (CC BY 4.0), from national weather service models.
For each route: a road-by-road overview (it works without a signal and prints), a button that opens the exact route in Google Maps on your phone, and full turn-by-turn directions from TomTom with live traffic. Download the maps for offline use before you need them. The overviews are written summaries; where they and the turn-by-turn differ, follow the turn-by-turn, and drive each route once before you need it.
A dose rate (R/h) only matters through the total dose you build up: rate × time. These tables turn the numbers on this page into what they mean for your body. For the gamma radiation from fallout, 1 R ≈ 1 rad ≈ 1 rem ≈ 10 mSv. The effects below are for the whole body receiving the dose within minutes to a few days, which is the fallout case.
| Total dose | What happens | Survival |
|---|---|---|
| under 5 R | No noticeable effect. A slight rise in lifetime cancer risk (about 1 in 400 extra at 5 R). For scale, natural background is about 0.3 R a year. | No effect on survival |
| 5 – 30 R | No symptoms. Lifetime cancer risk rises about 1–1.5 percentage points at the top of this range. | No effect on survival |
| 30 – 70 R | Mild symptoms possible in some people (nausea, tiredness). Blood counts dip for a few weeks and recover. | No deaths expected |
| 70 – 200 R | Radiation sickness begins. Nausea and vomiting within hours, then a symptom-free spell. Blood counts fall over the following weeks, raising infection risk. | Most recover; medical care helps |
| 200 – 500 R | Severe radiation sickness. Vomiting within an hour or two. Hair loss, bleeding and serious infections 2–4 weeks later. | From about 250–500 R, around half die within 60 days without medical care |
| 500 – 1,000 R | Very severe. Gut damage starts from about 600 R. | Most die within weeks, even with care |
| over 1,000 R | Gut and circulatory collapse. | Fatal, within days to 2 weeks |
Long term, each 100 R adds roughly 5 percentage points to lifetime risk of fatal cancer. The same total spread over weeks or months does much less immediate harm, because the body repairs between doses. Thresholds from CDC's clinical guidance on acute radiation syndrome (ARS begins above about 70 rad, mild symptoms from about 30 rad, LD50/60 about 250–500 rad, gut syndrome above about 1,000 rad).
Standing outdoors, unprotected, at a rate that does not change. Real fallout fades, falling to about a tenth for every 7× increase in time since the burst (see the calculator), so these times are the worst case for that reading.
Protection factors are typical values from US civil-defense guidance; the real value depends on the building. Driving through fallout counts as "in a car". Dust on skin and clothing adds to the dose, so brush off and wash when you get inside.
Every EPA gamma monitor in Tennessee, Arkansas, Oklahoma and Texas, plus the neighbouring monitors upwind of the two routes. Each chart is that monitor's dose rate over time, with its own 30-day median drawn as a dashed line — absolute numbers differ by site and mean nothing on their own, so the thing to watch is a line lifting away from its dashed baseline.
Read this before trusting a high number. Rainfall washes radon decay products out of the air and routinely pushes a monitor 50–100% above its baseline for a few hours. That is the most common cause of a spike by a wide margin, and it is local weather, not a plume. What would indicate something real is a sustained rise, at several monitors, moving downwind from one to the next, without rain to explain it. One station, briefly, on a wet day, is rain.
Readings are dose equivalent rate in nSv/h where the monitor reports it, otherwise gamma count rate in CPM. Breaks in a line are hours EPA has no reading for — gaps happen from telecoms outages and maintenance. The server checks EPA every 20 minutes and this page re-checks the server every 10, so a new EPA reading appears here within about half an hour of EPA publishing it.
A dose rate (R/h) is how fast radiation is hitting you. What harms you is the total dose: the rate multiplied by the time you are exposed. The same 1 R/h is harmless for a few minutes and dangerous for a few days. For fallout gamma rays, 1 R is about 1 rem, or 10 mSv. The figures below are for a whole-body dose received over a short time, a day or two, by a healthy adult. Children and pregnant women are more sensitive.
Time matters twice. First, fallout decays fast: its dose rate falls about tenfold for every sevenfold increase in time since the burst, so the first day holds most of the danger. Second, the body repairs itself. The same total dose spread over weeks does much less harm than taken in one day, which is why sheltering first and moving later works.
Rows are dose rate; columns are time spent in it. Each cell is the total dose, coloured by the effect bands above. This is the worst case: real fallout decays, so the true dose is lower. The calculator below accounts for decay.
Sources: CDC, Acute Radiation Syndrome, a fact sheet for clinicians; Glasstone & Dolan, The Effects of Nuclear Weapons (1977), ch. 9 and 12; ready.gov/radiation. Shelter factors are the usual civil-defense rough values; a real building can do better or worse. This is general information, not medical advice. After any real exposure, follow public-health instructions.