Sacramento is known for its hot summer weather, last year being no exception.
A report from the National Oceanic and Atmospheric Association found 2024 was California’s hottest on record, and weekly average temperatures last July in Sacramento were in the 90s.
But this summer so far has been a departure from expectations, especially last month. The capital city still saw plenty of sun in July but conditions felt distinctly cooler, with more days in the 80s than in the triple digits.
FOX40 Chief Meteorologist Adam Epstein sat down with CapRadio’s Chris Nichols to talk about the unusual summer surprise, the science behind it, and whether these conditions could return in the future.
This interview has been edited for length and clarity.
Interview highlights
What were some of the statistics behind this recent weather that stuck out to you?
Let's start with the mean maximum temperature. The average maximum temperature for this July was 89.4 degrees. That's about three degrees lower than the normal [of] 92.6. I'd also like to contrast this with last July where the mean average high was 98.5. So from last year to this year [there] was a huge difference.
This year was the seventh coolest when just looking at the high temperatures. But for meteorologists and statistics, we look at the highs and lows and average them all out. The mean average temperature came out to 73.5 degrees. The normal is 75.9.
Last year, it was 81 degrees. [That was] the warmest July ever and in fact… if you were here in July 2024, you could say you live through the warmest month in Sacramento's history.
What caused these cooler than expected temperatures last month?
We have to go into what's called synoptic meteorology. Synoptic is a scale. The same way you have microclimates, you have mesoscale meteorology and then synoptic scale, which you can think of as countrywide.
When we look at the Pacific during the summer time, there's a high pressure system that usually sits right off the coast of California called the Pacific High or the North Pacific High, more specifically. In typical patterns, high pressure acts like an invisible force field. Storms, areas of low pressure, can’t go through it, they get pushed around it.
Around highs, the winds spin clockwise and outward, so a low comes towards it from the west, gets pushed to the north towards the Gulf of Alaska, and then tends to drop in the Pacific Northwest, missing us completely. Now, this position of the high changed this summer. It shifted a bit farther to the north, and it's also a bit weaker.
All of a sudden, you have this pathway for lows to come directly to California that ushers in cooler air, creates more thunderstorm activity in the Sierra, and supports a more consistent marine layer at the coast. We had some fog hang around, even had some drizzle in San Francisco. Here in Sacramento the effects were one of the coolest July's in recent history.
I assume having a high pressure system further north is pretty unusual?
It is. Usually we have the typical pattern of the high right off the coast, and the heat. Around that high, when it's directly off the coast, you tend to get more north winds and that's a land breeze. The land breeze is warmer, [and] the sea breeze is cooler because of the ambient temperature above the ocean.
But you get a land breeze coming from the north… not only does it get hotter for us, but you also tend to get drier conditions and that leads to a more intense fire weather. So, we've been lucky on multiple fronts just feeling more comfortable, saving money on our electricity bills for air conditioning, and not having extreme fire danger yet this summer.
Did other parts of the west coast, or the country, feel this impact?
Not so much up in Oregon and Washington. At times, they still got into some heat, but California specifically was a lot cooler than normal - all the way down to Los Angeles and San Diego.
Meanwhile, the rest of the country was way hotter than normal. You had heatwaves through the Midwest and Chicago, down to the deep south, and it's not just the heat there but the humidity too. If you went to New York or to Florida, you have a temperature of 95-100 degrees, but it can feel like 115 with that humidity. Coming back to California, a high of 90 feels amazing.
We’ve all been enjoying the cooler weather, but it wasn’t quite record-breaking right?
When we just look at July, it's the 12th coolest on record. Didn’t even crack the top 10. There are other metrics we can look at. Summer, meteorologically speaking, is June, July, August… It's the hottest quarter of the year statistically. The mean average temperature so far for summer overall is 73 degrees, that's the 27th coolest on record. These records go back to 1947. Last year it was 78.2. That was the hottest start to record ever.
Our hottest temperature so far was just 102 degrees, that happened July 11. Coincidentally, that’s the first day the State Fair opened. The 100 degree days for the summer so far since June? Just two. We average 15 for a summer, so we are far behind that path. Last year at this date it was 20.
A temperature of 108 degrees is displayed on a bank sign in Sacramento, Calif., Wednesday, July 3, 2024.AP Photo/Rich PedroncelliIt has obviously been pretty dry, but what does rainfall look like for Sacramento in July?
An interesting fun fact about Sacramento in July is this is a month where we average 0.00 inches of rain. We expect nothing this month. And sure enough, that's what we got. This an effect of having that North Pacific high right off the coast, blocking any storms from coming our way.
In the summer, the only real chance we get of precipitation comes from monsoon moisture, which comes out of the Mexico region and then up through the four corner states. But if it drifts far enough west, it can get into the Sierra and then you get a couple of rogue storms that make their way into the Valley. So, it's possible that we get some thunderstorms in the next month or two, but it's not something you count on for a significant amount of moisture.
Should people expect to see a cool summer like this in future years, or was it just an anomaly?
Anytime we have cooler than normal conditions or a record cool, which is less and less frequent, I look back at this month and I think, “this very well may be the coolest July that we experienced for the rest of our lives.” Statistically, that's what the evidence points to.
Months in the summer, and all around the year, are getting warmer. For every one record cold event that we get, we get three or four record heat events. These things are becoming exceedingly rare in our changing climate, and I wouldn't expect us to see cooler July's. More often than not, they're going to be hotter than normal.
Temperatures have been climbing again. The forecast is calling for a return to the high 90s. Are we in for a dramatic shift back to hotter weather?
Weather is subjective and not objective in this regard. What's hot to you may not be hot to someone else. We are looking at a gradual warming trend this week, could be in the upper 90s by Saturday. That is more of what you'd expect for summer. It could be jarring to some if you got used to temperatures in the 80s to near 90s, which has been wonderful.
And beyond that, I honestly can't tell you what's going to happen. A lot of people have been asking me… since it hasn't been hot in June and July, does that mean we're going to make up for it in August and September? It's a common question [but] the answer is there's no indication.
What we have happening right now does not tell us what's going to happen later in the summer, does not tell us what’s going to happen later this winter. Weather doesn’t work that way.
Has the cooler weather helped curtail the risk of wildfires in Northern California?
It's called the energy release component… [it] basically tells us how much fuel is available for wildfires. The last time I looked at it, maybe 7-14 days ago, we were slightly below average for this time of year. So having the cooler conditions [and] not seeing north wind events definitely has helped.
Even though this year, California has burned more acres [statewide] than your five-year average, we still haven't seen any massive wildfires in Northern California. But as we go into August, September and even October, where vegetation dries out in the higher elevations in the mountains. That’s when the bigger wildfires become a concern. So hopefully that’s one lasting positive thing from our cooler summer.
