A chemical, biological, radiological, and nuclear weapon detection system is disclosed that heightens its acuity and alertness when it senses that a chemical, biological, radiological, or nuclear weapon attack is more likely. For example, it is well understood that a chemical gas attack is likely to be less effective when it is raining than when it is clear because the rain will suppress and dilute the chemical agent. Therefore, the likelihood of a chemical gas attack is higher when it is clear. In light of this and similar knowledge, the illustrative embodiment checks for evidence of an attack more frequently and with great acuity than when the ambient environmental (e.g., meteorological, etc.) characteristics (e.g., whether is it precipitating or not, whether it is sunny or not, etc) suggest that an attack is more likely. This enables the embodiment to conserve consumables that are used in detecting attacks for when the attacks are more likely.