The San Gabriel Valley is currently facing a significant increase in black fly activity, a problem that has been worsened by the recent record-breaking heat wave in Southern California. These tiny pests, known for their painful bites around the eyes and neck, are thriving due to the favorable conditions created by the intense heat and increased water flow from snow runoff. The San Gabriel Valley Mosquito and Vector Control District has issued an official warning to residents about the surge in black fly populations, noting that these flies can travel up to five miles from their breeding sites. The district is actively treating river breeding sites, but officials caution that it may take several weeks before these treatments significantly reduce the fly populations.