-- Heavy rain, thunder, lightening.
-- Heat index of 90 degrees. --learn more
-- Winter snow storms. Snow accumulation more than 1 inch.
-- Winter ice storms. Roads slippery.
-- Cold temperatures under 35 degrees.
-- Windy days, temps under 35 degrees.
Each member has their own definition of what is extreme, and should use their own discretion regarding canceling an event due to weather.
The same applies when deciding whether to attend an event that falls on a day of unusual weather.