Are you holding your seminars during the cold, rainy, snowy months of the year? Right now Northern California, where I live, is experiencing unusually bad weather. There is a possibility of lower attendance during stormy winter months but people do attend. Take an extra step to remind your audience of the event. Have your staff follow-up RSVPs with confirming phone calls and suggest alternate routes of travel, if necessary.
Double check that your venue is prepared attend to the needs of people who have made the effort to attend. They should have covered parking and parking valets so your guest don't have to get wet or cold while parking their cars and walking to the event. They should have ample room for checking coats, boots and umbrellas.
Be sure you and your staff appear relaxed, well-organized and professional throughout the event. If you are stressed because you are reacting to weather emergencies, your audience will be uncomfortable and not open to buying your products and services.
Read the articles on my website for further assistance on selecting a venue or a date for your seminar.