President Trump signs the wall during a visit with flood survivors of Hurricane Harvey at a relief center in Houston on Sept. 2. (Kevin Lamarque/Reuters)

President Trump’s average weekly approval rating in Gallup polling has ticked one percentage point upward over the past four weeks. Thirty-five, then 36, then 37 and now 38 percent of the country thinks that Trump is doing a good job.

Political observers would be justified in wondering why. Is this, perhaps, the effect of John F. Kelly stepping in to serve as chief of staff in the West Wing? Or is it the effect of Stephen K. Bannon moving back to his old job at Breitbart?

In the week since Kelly came in, there’s been effectively no change in Trump’s approval. That week it was 38 percent, then it fell and rose back to the same point. Since Bannon was ousted, the rise has been pretty consistent.

The change over the past four weeks has been heavily centered on the sorts of Americans that Trump would very much like to keep in line for 2020. Among college graduates, his approval has jumped 7 points; among those with advanced degrees, it’s up 10. Among moderate Republicans, his approval rating has climbed 7 points. In the case of moderate Republicans, he still is well behind where he was in January, but among better-educated Americans, he’s regained most of the ground he lost.

Perhaps some of this is a function of Bannon’s ouster. The removal of a controversial and nationalist figure from the president’s inner sanctum no doubt made many moderate Republicans happy. But there’s probably another, bigger reason: the hurricanes.

Google search interest in hurricanes exploded as Harvey and then Irma approached the continental United States. Trump is consistently one of the most-searched terms on Google, but he was dwarfed by interest in the storms.

At the same time, approval of Trump began to tick upward. (On the chart above, the left axis is Trump’s approval. The right is search interest, on Google’s proprietary scale.)

Let’s assume that moderate Republicans and those with more education are more likely to be skeptical of Trump. Over the course of his presidency, that’s certainly been the case. (In exit polling after the 2016 election, college graduates preferred Hillary Clinton to Trump by a 5-point margin and those with advanced degrees by a 21-point margin.) More attention paid to something other than Trump probably wouldn’t hurt him among those groups, and limiting Trump’s presidential activity to pronouncements about the effectiveness of the Federal Emergency Management Agency and visits to storm-torn regions probably wouldn’t either.

A quick aside: There has been a consistent question about whether Trump’s approval rating might drop into the low-30s — or below. One way of thinking about that question is by considering support for Trump before and after his inauguration. Looking at his support in general election polling as a percentage of the population on the whole (as opposed to just among registered or likely voters), he was pretty consistently in the low-30s when contrasted with Clinton.

On Election Day, Trump earned about 32.3 percent of the support of the over-18 population. (This is assuming that 70 percent of the population is registered to vote, which is the Census Bureau’s estimation.) In office, Trump’s poll numbers have generally been higher than that, though four weeks ago they were close.

Back to the point at hand. The new Gallup numbers mark the first time since he’s been president that his approval rating has increased three weeks in a row. If that’s largely a function of the hurricanes, that trend probably won’t last long (unless we keep getting more and more major hurricanes, which seems increasingly possible). If it’s something else, like the ouster of Bannon, there may be more room for Trump to grow.

Meaning that someday we might ask another hard-to-answer question: Is there an upper cap on his favorability?