Researchers regularly use large survey studies to examine public political opinion. Surveys running over days and months will necessarily incorporate religious occasions that can introduce variation in public opinion. Using recent survey data from Israel, this study demonstrates that giving surveys on religious occasions (e.g., the Sabbath, Hannukah, Sukkot) can elicit different opinion responses. These effects are found among both religious and non-religious respondents. While incorporating these fluctuations is realistic in longer-term surveys, surveys fielded in a short window inadvertently drawing heavily on a holiday or holy day sample may bias their findings. This study thus urges researchers to be cognizant of ambient religious context when conducting survey studies.