SAN FRANCISCO -- Despite those frigid nights, now is not the time to burn wood in fireplaces.

Officials with the Bay Area Air Quality Management District are asking residents not burn wood in their fireplaces or woodstoves on Thursday to prevent air quality from becoming unhealthy.

A winter Spare the Air alert is not in effect on Thursday and wood burning is not illegal, but strongly discouraged.

Winter Spare the Air Alerts were, however, issued on Tuesday and Wednesday.

Recommended no-burn days help to keep pollution levels from building to unhealthy levels, and may help to avoid calling a winter Spare the Air alert later in the week.

Contact Katie Nelson at 925-945-4780 or follow her at Twitter.com/katienelson210.