They aren’t.
Last year flu season began a little early. There’s always some variation. Look at the last 5 years and this year’s numbers are normal. Outside of flu season (typically October to March), flu cases drop dramatically. During the summer, there are fewer than 10 cases a week in the entire US. That happens every year. But there’s some variation in exactly when flu season begins and ends. Last year started early. This year it’s been picking up the past couple weeks. We’re up to 121 confirmed flu cases since the end of September. That’s typical.
https://www.cdc.gov/flu/about/season/flu-season.htm