Flight weather

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About these readings

Watches, warnings & advisories: Active National Weather Service alerts for the project coordinates, shown at the top when any are in force and omitted entirely when none are. A warning means the hazardous condition is occurring or imminent; a watch means conditions are favorable for it to develop; an advisory covers conditions that are inconvenient rather than dangerous. Colour follows that order — red, amber, blue. Alerts are polygon-based and issued for an area, so one can be in force across the county without affecting your specific site.
Wind & gust: The usual limiting factor. Gust matters more than sustained wind: a multirotor corrects continuously, and a gust that exceeds the aircraft's authority costs you position hold and battery at the same time. Reported at 10 m above ground — flow at altitude is normally stronger and less sheltered than the surface reading.
Temperature / dewpoint spread: The gap between air temperature and dewpoint, which is more useful than either number alone. A spread closing toward zero means the air is saturating: fog or low stratus is forming, and visibility can collapse quickly. A small spread near or below freezing also indicates icing potential. Highlighted at 4 °F or less.
Density altitude: The altitude the air feels like to a rotor, after correcting field elevation for pressure and temperature. High density altitude thins the air, so rotors generate less thrust: climb rate drops, payload margin shrinks, and endurance falls. On a hot afternoon at these elevations it commonly runs thousands of feet above the ground you are standing on, which is the failure mode that surprises pilots trained at lower elevation. Computed for the project site, not the reporting station. Highlighted when it exceeds site elevation by 2,000 ft or more.
Ceiling & maximum altitude: Ceiling is the lowest broken or overcast layer; scattered and few layers are not ceilings. Which cloud rule applies depends on how you are operating, and the badge beside the coordinates shows which set this page is using.
COA / part 91 (default). COA 2025-WSA-16323 authorizes Class G operations at or below 1,199 ft AGL. Under 14 CFR 91.155, Class G at or below 1,200 ft AGL by day requires 1 statute mile visibility and remaining clear of clouds, so the ceiling itself becomes the cap when it falls below 1,199 ft. Night minimums are higher.
Part 107. 400 ft AGL, 3 statute miles, and 500 ft below the clouds — add rule=107 to the URL to use these instead.
Either way the COA altitude applies in Class G only, and this page does not check which airspace the site sits in. Override the ceiling with the alt parameter.
Visibility: Threshold follows the rule set in force: 1 statute mile for daytime Class G under 91.155, 3 statute miles under 107.51. Highlighted below the applicable figure.
Weather minimums inside a TFR: The COA waives 91.155 only for operations conducted within a 91.137 TFR, where the incident or on-scene commander is responsible for airspace segregation and deconfliction between manned and unmanned aircraft. Outside a TFR the standard minimums above apply, and this page always displays the unwaived thresholds.
Icing watch-out: Flags hours where the forecast temperature is at or below 35 °F with a temperature/dewpoint spread of 4 °F or less — freezing conditions plus enough moisture for ice to form on the airframe. Ice on rotors destroys lift and adds weight faster than most airframes can compensate, and small unmanned aircraft carry no anti-ice or de-ice equipment. The lower bound is −4 °F, below which the air generally holds too little moisture for meaningful accretion. The value shown is the coldest hour in the run.
Heavy precipitation watch-out: Flags hours where forecast precipitation exceeds 0.30 in/hr, the conventional boundary above moderate rain. Light and moderate precipitation are not flagged here, though they still end most mapping missions. Derived from the gridded quantitative precipitation forecast, converted to an hourly rate: the forecast is issued in multi-hour blocks, so the value is the average rate across the block rather than a peak within it. Adjust with the heavy URL parameter.
Precipitation: Accumulation in the past hour at the reporting station. Most airframes are not rated for flight in precipitation, and water on the lens ends a mapping mission regardless of what the aircraft tolerates.
Kp index: Planetary geomagnetic activity, 0–9. Elevated Kp disturbs the ionosphere and degrades GNSS accuracy, which matters more for PPK and RTK survey work than for ordinary flight: it lengthens time to fix and can leave you with float rather than fixed solutions. Kp 5 and above is storm level and is highlighted. Below about 4 it is not worth thinking about.
Sun & lighting: Under the COA these times are a lighting trigger, not a hard stop. The Certificate of Waiver requires anti-collision lighting for civil twilight and night operations to increase the conspicuity of the aircraft, and the system must be operational at all times, day or night, unless operating in a TFR — the CoW waives 91.209(a)(1) only inside a TFR. A reminder appears here when the current time falls outside sunrise to sunset. Sun angle also drives shadow length: low-sun imagery produces long shadows and weaker tie points in photogrammetric processing. Computed from the site coordinates and today's date.
Before you fly: Not weather, but on the same checklist. The COA requires a Distant (D) NOTAM not less than 24 hours and not more than 72 hours in advance of routine operations, cancelled when the operation is complete; first responder and prescribed fire operations may file as soon as practicable. Airport standoffs are 5 NM from a towered airport, 3 NM from an airport with a published instrument procedure, 2 NM otherwise, and 2 NM from a heliport. MTR and SUA deconfliction is the operator's responsibility.
Low temperature threshold: Set at 32 °F, freezing, because that is where the equipment gate actually sits: the X10 will not launch with a battery below 0 °C, and the Astro wants batteries above 10 °C at takeoff. Sun does little to close the gap — a grey case in full winter sun and still air gains only about 9 °F over ambient, so reaching the launch minimum by solar gain alone needs ambient near 23 °F, and any breeze erases most of that. Treat this row as notice that batteries need pre-warming and that endurance will be down, not as a no-fly call. It will fire on most winter mornings. Adjust with the cold URL parameter.
High temperature threshold: Set at 85 °F because the limiting factor is equipment, not crew comfort. A black battery left in still air under full sun runs roughly 40–60 °F above ambient at equilibrium, which puts it near the Astro's 50 °C (122 °F) ceiling somewhere between the low seventies and ninety, centred around eighty — so the threshold sits at the lower edge of that band rather than above it. The thermal time constant is around twenty minutes, so brief exposure is harmless and a full mission's worth is not. Shade spare batteries rather than trusting the ambient reading. Adjust with the heat URL parameter.
Forecast sections: Watch-outs and the day/night outlook come from the National Weather Service gridded forecast for the project coordinates. Current conditions come from the nearest station that is reporting, which may be a considerable distance and elevation away.