Meteors streaked over Arizona at about 40 a second for 20 minutes one November night in 1966, from the same shower that returns every November

McLean’s observing record shows how quickly the shower intensified before the main storm. From 08:30 to 09:30 UTC on November 17, the Kitt Peak team counted 33 Leonids in an hour. A single observer recorded 192 between 09:50 and 10:50 UTC, and by 11:10 UTC the rate had reached at least 30 per minute and was increasing rapidly.

At 11:54 UTC, the observed rate reached 40 meteors per second. McLean wrote that this rate persisted for about 20 minutes before falling to 30 per minute by 12:40 UTC. Forty meteors per second corresponds to 2 400 meteors per minute during that observed peak interval.

The 40-per-second figure was a peak rate recorded by the observing team at Kitt Peak, not a uniform average for the whole state of Arizona or for the entire night. McLean reported that observers made counts and magnitude estimates for different regions of the sky, with the rate changing sharply over the course of the observation.

McLean also photographed the shower continuously after 11:00 UTC using a Pentax camera at f/2. He obtained 18 useful frames on 35 mm Tri-X film, with the highest photographic rate reaching one meteor per second on a frame exposed for 43 seconds.

The photographic count was much lower than the visual count because the camera sampled a smaller area of sky and did not record meteors as faint as those visible to the eye. McLean estimated an observer’s visual field at about 9 500 square degrees compared with about 950 square degrees for the camera, a difference of roughly ten to one before the greater sensitivity of human vision was considered.

The count-rate curve in the paper places the pronounced maximum between about 11:30 and 12:30 UTC. Using the time width of that maximum and Earth’s orbital velocity, McLean estimated the well-defined width of the dense meteoroid swarm at approximately 32 000 km (19 900 miles), about 2.5 times Earth’s diameter.

The Leonids return every November because Earth repeatedly crosses streams of debris associated with comet 55P/Tempel-Tuttle. Dust and small particles released from the comet remain distributed along its orbit, and their encounters with Earth’s atmosphere produce the annual shower. Tempel-Tuttle itself takes about 33 years to complete one orbit around the Sun.

Leonid particles enter the atmosphere at about 70 km/s (44 miles/s), making the shower one of the fastest major annual meteor streams. Their paths are nearly parallel in space, but perspective makes them appear to spread outward from a point in the constellation Leo known as the radiant, which gives the Leonids their name.

The distinction between a meteor shower and a meteor storm is one of rate. NASA uses at least 1 000 meteors per hour as the threshold for a meteor storm and describes the 1966 Leonids as producing thousands of meteors per minute during the most intense part of the event.

Modern summaries do not all give the intense interval the same duration. NASA describes thousands of meteors per minute during a 15-minute period, while McLean’s primary Kitt Peak report states that the observed rate reached 40 per second and persisted for about 20 minutes. The latter is the direct source for the 20-minute figure in the historical account.

The annual return in November 2026 is expected to be far less intense. NASA/JPL’s November skywatching guidance recommends the early morning hours of November 17 and 18, after the Moon sets, and says ideal conditions could produce around 15 meteors per hour, with most observers seeing fewer.

That modern figure is a viewing forecast for an ordinary annual return rather than a prediction of another 1966-style storm. At 15 meteors per hour, the average interval under ideal conditions would be about four minutes between meteors, while the Kitt Peak team recorded dozens every second during the short 1966 maximum. The figures come from different observing contexts, but the scale of the contrast is clear.

The wide difference between an ordinary Leonid return and a storm arises because material along the comet’s debris stream is not distributed uniformly. Earth crosses Leonid debris every year, but an encounter with a much denser concentration of particles can transform the annual shower into a brief meteor storm.

The 1966 Kitt Peak record is unusually useful because it preserves that transition in measured rates: dozens per hour, then hundreds per hour, then dozens per minute, and finally dozens per second. The Leonids returning in November 2026 come from the same parent stream, but current NASA guidance describes an ordinary annual display rather than a repeat of the storm measured over Arizona six decades ago.

References:

¹ McLean, D. R. (1967). The Leonid meteor shower of November 17, 1966. Communications of the Lunar and Planetary Laboratory, 6, 43-48. University of Arizona Space Imagery Center – April 15, 1967

² Leonids Meteor Shower – NASA Science – accessed November 11, 2026

³ What’s Up: November 2026 Skywatching Tips from NASA – NASA Science – November 2, 2026