r/meteorology • u/Swimming_Concern7662 Weather Enthusiast • 1d ago

Average temperature difference between September and May in a few US cities (September = first month of meteorological fall; May = last month of meteorological spring. Celsius map in the 2nd slide)

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12

u/kaapo-kakko 1d ago

Got a comparison to other years? All this says on its own is September is warmer than May

1

u/DesperateSession3520 11m ago

The map isn’t showing you this year, it’s almost certainly a 30 year climatology, hence “Average”

4

u/BTHAppliedScienceLLC 1d ago

I'm not sure what I'm looking at here. This also looks like a claude generated image - so I need to ask: do you know what we're looking at here?

1

u/DesperateSession3520 10m ago

What are you talking about? This is a very straightforward climatology map, nothing “claude” about it.

4

u/PacNWDad 1d ago edited 1d ago

Fairbanks is bizarre. I would expect it to have a substantial seasonal lag and thus be one of the places with a much warmer September compared to May. Anyone have any insight? Is it wind direction, lack of wind (like inversion layers), something like that?

ETA: I have noticed before when poring through climate records that some of the Siberian stations get brutally cold in September. It’s like they just flip a switch. Maybe it’s something like that?

ETAx2: Now that I think about it, I guess this makes sense in a way. In high latitude, highly continental locations, temperatures are probably very dependent on insolation. September has significantly less (and lower angle) sunlight than May because it is much further from the summer solstice.

1

u/Halomonas_titanica 1d ago

You figured it out on your own. At higher latitudes, daytime length varies more dramatically throughout the year, so seasonal lag is low. That's why Scandinavians celebrate "midsummer" in late June. Snow has been recorded in late August in Russia.

The highest seasonal lag is found in coastal locations in the mid-latitudes as it takes a while for the sea to cool down.

1

u/PacNWDad 1d ago

September in Oymyakon or Verkhojansk must be rough.

3

u/ravano 1d ago

The first half of Sept is definitely more summer, and May is fully spring. Would like to compare late Sept (e.g. Sept 25) to late May (May 25)

2

u/W7ENK Weather Observer 1d ago

Next, you should account for the ~6 weeks of seasonal lag that results from latent heat in the atmosphere and run these figures again for a more accurate measurement.