Over the years I have observed these Sporadic E-Skip characteristics
1. Rapid fading to full local strength in seconds.
2. Depending on the frequency, mileage can vary. On the FM broadcast band, sporadic E-Skip can average 800 to 1,200 miles +/-. On six meters this can be from 500 to 1,000 miles +/-. On 10 meters the range can be even be lower from 350 miles to 1,000 miles. My record for short skip was about 300 miles from Pittsburgh PA to Northern NJ some 25 years ago.
3. Sporadic E-Skip generally has a season that runs from May until early August, and again from December through January. (Although it can happen anytime)
4 . Time for sporadic E-Skip seems to be 8 to 10 AM and again from 11 AM to 1 PM and with a bigger peak in the afternoon from 4 PM till 8 PM or longer depending on the band. (All day openings are certainly possible)
5. Multi-hop Sporadic E-Skip is not only possible but can be common on 6 meters and below with openings across the 'pond' or to the West Coast from the East Coast. Multi-hop sporadic e-skip on the FM broadcast band is pretty rare but it has happened with FM broadcast stations from the U.S. and Canadian east coast being picked up in Europe.
6. While the MUF can go into the FM broadcast band , 88 - 108 mhz. It can go much higher into the two meter band and even on occasion reach the 220 Mhz band.