Until Thursday, Minnesota was experiencing a relatively quiet year for tornadoes. Much of the summer season was too hot for spinning "supercell" storms capable of twisters. But Thursday was ripe with wind shear and extreme instability. Tornado watches and warnings went out in a timely fashion. It's a minor miracle that there were no serious injuries (or worse) from the five confirmed tornadoes south of the Twin Cities.

In severe weather elsewhere, meteorologists are arguing that the Saffir-Simpson scale used to rate hurricanes needs an overhaul. Florence was downgraded to a Category 1. Many locals mistakenly believed they could ride out the storm, only to need rescuing. The scale takes winds into account but not the size of the storm surge or quantity of rain expected.

Back home, a fine Sunday gives way to T-storms late Monday. Another round of rain comes Thursday, and next weekend may be sloppy and wet.

Canadian air stays north of the border for now; the Twin Cities should be frost-free into the first week of October.