Federal employment numbers are on a general upswing after hitting a low period in 2014, but federal workers should expect to see an increase in the ranks of their colleagues this summer as the regular seasonal employment spike hits many agencies.

According to Office of Personnel Management data, the federal workforce has increased by an average of about 1 percent in June of the last five years.

A 1 percent increase may not sound like much, but, considering the over 2.1 million feds that currently work for the federal government, that’s approximately 21,000 new government workers coming on board.

Part of the increase stems from seasonal, or non-permanent positions, which have increased by an average of about 16 percent each summer.

Some of that change can be accounted for by the influx of college and high school graduates entering the federal workforce after finishing school. The federal workforce under 30 years old spikes an average of 10 percent between March and June.

But certain federal agencies experience more precise increases in workforce need each summer.

The Department of Agriculture experiences an employee increase of about 13 percent each year, generally in the Forest Service.

According to a USDA spokesperson, the hiring increases primarily come from the bulk hiring of firefighters and fire-suppression workers to help combat the increased likelihood of wildfires in the summer months. These hires predominantly occur in the western United States, where wildfires are most common.

The Department of Interior also experiences a 13 percent employee increase on average over the summer, and according to an Interior spokesperson, similarly needs the increased manpower to address anticipated wildfires in that season.

The agency also hires more employees in the National Parks to meet the demand of American families that are more likely to visit during the summer.

But the demand during wildfire season may not be as defined an uptick in future years as it has been in the past.

According to the USDA spokesperson, changing global weather patterns have meant that what was a defined season 10 years ago isn’t even called “wildfire season” anymore by agency officials, because fires are happening more frequently outside the established timeframe.

And not all agencies experience a summer increase. The Department of Defense workforce decreases by about 5 percent each June, predominantly in the Defense Education Activity, which manages schools for the children of servicemen and women.

With a workforce of over 100,000, that averages to about 5,000 fewer DoD employees each summer, which are then regained in the fall.

“Our schools are staffed with hundreds of local hired positions that are seasonal. When school is in recess for the summer, many of those positions are vacated due to permanent change of station and all of them are in a non-pay status over the summer,” Department of Defense Spokeswoman Lt. Col. Carla Gleason told Federal Times.

“Also, not all of our teachers elect to be paid over the summer so it would appear as less staff/payroll over the summer months. Teachers work 190 days but can elect to spread their pay over 26 pay periods for a consistent income throughout the year.”