During April, the City of Longmont will test the Outdoor Emergency Warning System EVERY MONDAY at 10 am for the entire month – April 4, 11, 18 and 25.This siren will last two to four minutes. If the weather is bad on one of these dates, the test will not be held. In May, June, July and August testing of the outdoor warning sirens will return to the regular once-a-month schedule at 10 am on the first Monday of the month. If you hear the siren and it isn’t during a testing period, seek immediate cover and tune to a metro Denver radio or television station for information. Please do not call 911 unless you need immediate assistance.